Removing roman number after the title page

Question

How can I get rid of this roman number II? The page happens to be the second one, i.e., the one that comes after the Title Page.

This is how my main.tex looks like:

% Set up the document
\documentclass[a4paper, 11pt, oneside]{Thesis}  % Use the "Thesis" style, based on the ECS Thesis style by Steve Gunn
%
% Put your figures in this directory
\graphicspath{Figures/}  % Location of the graphics files (set up for graphics to be in PDF format)
%

% Include any extra LaTeX packages required
\usepackage[square, numbers, comma, sort&compress]{natbib}  % Use the "Natbib" style for the references in the Bibliography
\usepackage{verbatim}  % Needed for the "comment" environment to make LaTeX comments
\usepackage{vector}  % Allows "\bvec{}" and "\buvec{}" for "blackboard" style bold vectors in maths
\hypersetup{urlcolor=blue, colorlinks=true}  % Colours hyperlinks in blue, but this can be distracting if there are many links.

%% ----------------------------------------------------------------
\begin{document}
\frontmatter      % Begin Roman style (i, ii, iii, iv...) page numbering

%
\UNIVERSITY{{THE UNIVERSITY OF MELBOURNE }}    
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Update your department and school here:
\department{{Department of Mad Science}}
\school{{Melbourne School of Awesome}}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Set up the Title Page
% Change your thesis title and your information here
\title  {Thesis Title}
\authors  {\texorpdfstring
            {\href{your web site or email address}{Author Name\\ \small ORCID: }}
            {Author Name}
            }
\addresses  {\groupname\\\deptname\\\univname}  % Do not change this here, instead these must be set in the "Thesis.cls" file, please look through it instead
\date       {\today}
\subject    {}
\keywords   {}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\maketitle
%% ----------------------------------------------------------------

\setstretch{1.3}  % It is better to have smaller font and larger line spacing than the other way round

% Define the page headers using the FancyHdr package and set up for one-sided printing
\fancyhead{}  % Clears all page headers and footers
\rhead{\thepage}  % Sets the right side header to show the page number
\lhead{}  % Clears the left side page header

\pagestyle{fancy}  % Finally, use the "fancy" page style to implement the FancyHdr headers

%% ----------------------------------------------------------------
% The Abstract Page
\input{Preamble/Abstract.tex}
\clearpage  % Abstract ended, start a new page

%% ----------------------------------------------------------------
% Declaration Page required for the Thesis, your institution may give you a different text to place here
\input{Preamble/Declaration.tex}
\clearpage  % Declaration ended, now start a new page

%% ----------------------------------------------------------------
% Preface Page required for the Thesis, your institution may give you a different text to place here
\input{Preamble/Preface.tex}
\clearpage  % Preface ended, now start a new page

%% ----------------------------------------------------------------
% The Acknowledgements page, for thanking everyone
\setstretch{1.3}  % Reset the line-spacing to 1.3 for body text (if it has changed)
\input{Preamble/Acknowledgements.tex}
\clearpage  % End of the Acknowledgements
%% ----------------------------------------------------------------

\pagestyle{fancy}  %The page style headers have been "empty" all this time, now use the "fancy" headers as defined before to bring them back


%% ----------------------------------------------------------------
\lhead{\emph{Contents}}  % Set the left side page header to "Contents"
\tableofcontents  % Write out the Table of Contents

%% ----------------------------------------------------------------
\lhead{\emph{List of Figures}}  % Set the left side page header to "List if Figures"
\listoffigures  % Write out the List of Figures

%% ----------------------------------------------------------------
\lhead{\emph{List of Tables}}  % Set the left side page header to "List of Tables"
\listoftables  % Write out the List of Tables

%% ----------------------------------------------------------------
\setstretch{1.5}  % Set the line spacing to 1.5, this makes the following tables easier to read
\clearpage  % Start a new page
\lhead{\emph{Abbreviations}}  % Set the left side page header to "Abbreviations"
\listofsymbols{ll}  % Include a list of Abbreviations (a table of two columns)
{
% \textbf{Acronym} & \textbf{W}hat (it) \textbf{S}tands \textbf{F}or \\
\textbf{LAH} & \textbf{L}ist \textbf{A}bbreviations \textbf{H}ere \\

}

%% ----------------------------------------------------------------
\clearpage  % Start a new page
\lhead{\emph{Constants}}  % Set the left side page header to "Physical Constants"
\listofconstants{lrcl}  % Include a list of Physical Constants (a four column table)
{
% Constant Name & Symbol & = & Constant Value (with units) \\
Speed of Light & $c$ & $=$ & $2.997\ 924\ 58\times10^{8}\ \mbox{ms}^{-\mbox{s}}$ (exact)\\

}

%% ----------------------------------------------------------------
\clearpage  %Start a new page
\lhead{\emph{Symbols}}  % Set the left side page header to "Symbols"
\listofnomenclature{lll}  % Include a list of Symbols (a three column table)
{
% symbol & name & unit \\
$a$ & distance & m \\
$P$ & power & W (Js$^{-1}$) \\
& & \\ % Gap to separate the Roman symbols from the Greek
$\omega$ & angular frequency & rads$^{-1}$ \\
}
%% ----------------------------------------------------------------
% End of the pre-able, contents and lists of things


%% ----------------------------------------------------------------
\mainmatter   % Begin normal, numeric (1,2,3...) page numbering
\pagestyle{fancy}  % Return the page headers back to the "fancy" style

% Include the chapters of the thesis, as separate files
% Just uncomment the lines as you write the chapters

\input{Chapters/Chapter1} % Introduction

%\input{Chapters/Chapter2} % Background Theory 

%\input{Chapters/Chapter3} % Experimental Setup

%\input{Chapters/Chapter4} % Experiment 1

%\input{Chapters/Chapter5} % Experiment 2

%\input{Chapters/Chapter6} % Results and Discussion

%\input{Chapters/Chapter7} % Conclusion

%% ----------------------------------------------------------------
% Now begin the Appendices, including them as separate files

\addtocontents{toc}{\vspace{2em}} % Add a gap in the Contents, for aesthetics

\appendix % Cue to tell LaTeX that the following 'chapters' are Appendices

\input{Appendices/AppendixA}    % Appendix Title

%\input{Appendices/AppendixB} % Appendix Title

%\input{Appendices/AppendixC} % Appendix Title

\addtocontents{toc}{\vspace{2em}}  % Add a gap in the Contents, for aesthetics
\backmatter

%% ----------------------------------------------------------------
\label{Bibliography}
\lhead{\emph{Bibliography}}  % Change the left side page header to "Bibliography"
\bibliographystyle{unsrtnat}  % Use the "unsrtnat" BibTeX style for formatting the Bibliography
\bibliography{Bibliography}  % The references (bibliography) information are stored in the file named "Bibliography.bib"

\end{document}  % The End
%% ----------------------------------------------------------------

UPDATED: THESIS.CLS

   %%
%% Modified by Ricardo Garcia-Rosas to satisfy the rules established by the University of Melbourne's Research Higher Degrees Committee as of 4th of June 2019.
%% Guidelines can be found at: https://gradresearch.unimelb.edu.au/__data/assets/pdf_file/0004/2027839/Preparation-of-GR-theses-rules.pdf
%%
%% Original header:
%%
%% This is file `Thesis.cls', based on 'ECSthesis.cls', by Steve R. Gunn
%% generated with the docstrip utility.
%%
%% Created by Steve R. Gunn, modified by Sunil Patel: www.sunilpatel.co.uk

\NeedsTeXFormat{LaTeX2e}[1996/12/01]
\ProvidesClass{Thesis}
[2007/22/02 v1.0
LaTeX document class]
\def\baseclass{book}
\DeclareOption*{\PassOptionsToClass{\CurrentOption}{\baseclass}}
\def\@checkoptions#1#2{
    \edef\@curroptions{\@ptionlist{\@currname.\@currext}}
    \@tempswafalse
    \@tfor\@this:=#2\do{
        \@expandtwoargs\in@{,\@this,}{,\@curroptions,}
        \ifin@ \@tempswatrue \@break@tfor \fi}
    \let\@this\@empty
    \if@tempswa \else \PassOptionsToClass{#1}{\baseclass}\fi
}
\@checkoptions{11pt}{{10pt}{11pt}{12pt}}
\PassOptionsToClass{a4paper}{\baseclass}
\ProcessOptions\relax
\LoadClass{\baseclass}
\newcommand\bhrule{\typeout{------------------------------------------------------------------------------}}



\newcommand\Declaration[1]{
    \btypeout{Declaration of Authorship}
    \addtotoc{Declaration of Authorship}
    \thispagestyle{plain}
    \null\vfil
    %\vskip 60\p@
    \begin{center}{\huge\bf Declaration of Authorship\par}\end{center}
    %\vskip 60\p@
    {\normalsize #1}
    \vfil\vfil\null
    %\cleardoublepage
}

\newcommand\Preface[1]{
    \btypeout{Preface}
    \addtotoc{Preface}
    \thispagestyle{plain}
    \null\vfil
    %\vskip 60\p@
    \begin{center}{\huge\bf Preface\par}\end{center}
    %\vskip 60\p@
    {\normalsize #1}
    \vfil\vfil\null
    %\cleardoublepage
}

\newcommand\btypeout[1]{\bhrule\typeout{\space #1}\bhrule}
\def\today{\ifcase\month\or
    January\or February\or March\or April\or May\or June\or
    July\or August\or September\or October\or November\or December\fi
    \space \number\year}
\usepackage{setspace}
\onehalfspacing
\setlength{\parindent}{0pt}
\setlength{\parskip}{2.0ex plus0.5ex minus0.2ex}

%\usepackage{vmargin}
%\setmarginsrb           { 1.5in}  % left margin
%{ 0.6in}  % top margin
%{ 1.0in}  % right margin
%{ 0.8in}  % bottom margin
%{  20pt}  % head height
%{0.25in}  % head sep
%{   9pt}  % foot height
%{ 0.3in}  % foot sep
\raggedbottom
\setlength{\topskip}{1\topskip \@plus 5\p@}
\doublehyphendemerits=10000       % No consecutive line hyphens.
\brokenpenalty=10000              % No broken words across columns/pages.
\widowpenalty=9999                % Almost no widows at bottom of page.
\clubpenalty=9999                 % Almost no orphans at top of page.
\interfootnotelinepenalty=9999    % Almost never break footnotes.
\usepackage{fancyhdr}
\lhead[\rm\thepage]{\fancyplain{}{\sl{\rightmark}}}
\rhead[\fancyplain{}{\sl{\leftmark}}]{\rm\thepage}
\chead{}\lfoot{}\rfoot{}\cfoot{}
\pagestyle{fancy}
\renewcommand{\chaptermark}[1]{\btypeout{\thechapter\space #1}\markboth{\@chapapp\ \thechapter\ #1}{\@chapapp\ \thechapter\ #1}}
\renewcommand{\sectionmark}[1]{}
\renewcommand{\subsectionmark}[1]{}
\def\cleardoublepage{\clearpage\if@twoside \ifodd\c@page\else
    \hbox{}
    \thispagestyle{empty}
    \newpage
    \if@twocolumn\hbox{}\newpage\fi\fi\fi}
\usepackage{amsmath,amsfonts,amssymb,amscd,amsthm,xspace}
\theoremstyle{plain}
\newtheorem{example}{Example}[chapter]
\newtheorem{theorem}{Theorem}[chapter]
\newtheorem{corollary}[theorem]{Corollary}
\newtheorem{lemma}[theorem]{Lemma}
\newtheorem{proposition}[theorem]{Proposition}
\newtheorem{axiom}[theorem]{Axiom}
\theoremstyle{definition}
\newtheorem{definition}[theorem]{Definition}
\theoremstyle{remark}
\newtheorem{remark}[theorem]{Remark}
\usepackage[centerlast,small,sc]{caption}
\setlength{\captionmargin}{20pt}
\newcommand{\fref}[1]{Figure~\ref{#1}}
\newcommand{\tref}[1]{Table~\ref{#1}}
\newcommand{\eref}[1]{Equation~\ref{#1}}
\newcommand{\cref}[1]{Chapter~\ref{#1}}
\newcommand{\sref}[1]{Section~\ref{#1}}
\newcommand{\aref}[1]{Appendix~\ref{#1}}
\renewcommand{\topfraction}{0.85}
\renewcommand{\bottomfraction}{.85}
\renewcommand{\textfraction}{0.1}
\renewcommand{\dbltopfraction}{.85}
\renewcommand{\floatpagefraction}{0.75}
\renewcommand{\dblfloatpagefraction}{.75}
\setcounter{topnumber}{9}
\setcounter{bottomnumber}{9}
\setcounter{totalnumber}{20}
\setcounter{dbltopnumber}{9}
\usepackage{graphicx}
\usepackage{epstopdf}
%\usepackage[scriptsize]{subfigure}
\usepackage{booktabs}
\usepackage{rotating}
\usepackage{listings}
\usepackage{lstpatch}
\lstset{captionpos=b,
    frame=tb,
    basicstyle=\scriptsize\ttfamily,
    showstringspaces=false,
    keepspaces=true}
\lstdefinestyle{matlab} {
    language=Matlab,
    keywordstyle=\color{blue},
    commentstyle=\color[rgb]{0.13,0.55,0.13}\em,
    stringstyle=\color[rgb]{0.7,0,0} }
\usepackage[pdfpagemode={UseOutlines},bookmarks=true,bookmarksopen=true,
bookmarksopenlevel=0,bookmarksnumbered=true,hypertexnames=false,
colorlinks,linkcolor={blue},citecolor={blue},urlcolor={red},
pdfstartview={FitV},unicode,breaklinks=true]{hyperref}
\pdfstringdefDisableCommands{
    \let\\\space
}
\newcommand*{\supervisor}[1]{\def\supname{#1}}
\newcommand*{\examiner}[1]{\def\examname{#1}}
\newcommand*{\degree}[1]{\def\degreename{#1}}
\newcommand*{\authors}[1]{\def\authornames{#1}}
\newcommand*{\addresses}[1]{\def\addressnames{#1}}
\newcommand*{\university}[1]{\def\univname{#1}}
\newcommand*{\UNIVERSITY}[1]{\def\UNIVNAME{#1}}
\newcommand*{\school}[1]{\def\schoolname{#1}}
\newcommand*{\SCHOOL}[1]{\def\SCHOOLNAME{#1}}
\newcommand*{\group}[1]{\def\groupname{#1}}
\newcommand*{\GROUP}[1]{\def\GROUPNAME{#1}}
\newcommand*{\department}[1]{\def\deptname{#1}}
\newcommand*{\DEPARTMENT}[1]{\def\DEPTNAME{#1}}
\newcommand*{\subject}[1]{\def\subjectname{#1}}
\newcommand*{\keywords}[1]{\def\keywordnames{#1}}
\supervisor  {}
\examiner    {}
\degree      {Doctor of Philosophy}
\authors     {}
\university  {\texorpdfstring{\href{University Web Site URL Here (include http://)}
        {The University of Melbourne}}
    {The University of Melbourne}}
\UNIVERSITY  {\texorpdfstring{\href{University Web Site URL Here (include http://)}
        {THE UNIVERSITY OF MELBOURNE}}
    {THE UNIVERSITY OF MELBOURNE}}
\school  {\texorpdfstring{\href{School Web Site URL Here (include http://)}
        {School Name}}
    {School Name}}
\SCHOOL  {\texorpdfstring{\href{School Web Site URL Here (include http://)}
        {SCHOOL NAME (IN BLOCK CAPITALS)}}
    {SCHOOL NAME (IN BLOCK CAPITALS)}}
\group       {\texorpdfstring{\href{Research Group Web Site URL Here (include http://)}
        {Research Group Name}}
    {Research Group Name}}
\GROUP       {\texorpdfstring{\href{Research Group Web Site URL Here (include http://)}
        {RESEARCH GROUP NAME (IN BLOCK CAPITALS)}}
    {RESEARCH GROUP NAME (IN BLOCK CAPITALS)}}
\department     {\texorpdfstring{\href{Department Web Site URL Here (include http://)}
        {Department Name}}
    {Department Name}}
\DEPARTMENT     {\texorpdfstring{\href{Department Web Site URL Here (include http://)}
        {DEPARTMENT NAME (IN BLOCK CAPITALS)}}
    {DEPARTMENT NAME (IN BLOCK CAPITALS)}}
\addresses   {}
\subject     {}
\keywords    {}
\renewcommand\maketitle{
    \btypeout{Title Page}
%   \hypersetup{pdftitle={\@title}}
%   \hypersetup{pdfsubject=\subjectname}
    \hypersetup{pdfauthor=\authornames}
%   \hypersetup{pdfkeywords=\keywordnames}
    \thispagestyle{empty}
    \begin{titlepage}
        \let\footnotesize\small
        \let\footnoterule\relax
        \let \footnote \thanks
        \setcounter{footnote}{0}
        \null
        \vskip 0\p@
        \begin{center}
            \setlength{\parskip}{0pt}
            %
            %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
            % Comment \includegraphics line out!!
            %
            \vspace{-1.5cm}         
            {\includegraphics[width=0.5\textwidth]{Figures/escudo_universidad}}
            %
            %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
            %
%       \noindent\rule{\textwidth}{1.3pt}\vspace{0.8cm}
            \vspace{4cm}
            
            {\Huge \bf \begin{spacing}{1} \@title \end{spacing} \par}
            \vspace{5cm}
            {\LARGE \authornames \par}
            \vspace{5cm}
            {\large A Work Submitted for the Degree of  \par}
            {\large Data Science Specialist at \UNIVNAME \par}
%           {\large \schoolname \par}
            \bigskip
            {\Large \@date \par}
            \bigskip
        \end{center}
        \par
        \@thanks
        \vfil\null
    \end{titlepage}
    \setcounter{footnote}{0}%
    \global\let\thanks\relax
    \global\let\maketitle\relax
    \global\let\@thanks\@empty
    \global\let\@author\@empty
    \global\let\@date\@empty
    \global\let\@title\@empty
    \global\let\title\relax
    \global\let\author\relax
    \global\let\date\relax
    \global\let\and\relax
    \cleardoublepage
}
\newenvironment{abstract}
{
    \btypeout{Abstract Page}
    \thispagestyle{empty}
    \null\vfil
    \begin{center}
        \setlength{\parskip}{0pt}
        {\large \textbf{Blablabalbalbalbalbalablabalbalablabalbalbala} \par}
        \bigskip
        \bigskip
        \bigskip
        {\normalsize{\textbf{Abstract}} \par}
%       \bigskip
%       {\normalsize \deptname \par}
%       {\normalsize \schoolname \par}
%       \bigskip
%       {\normalsize Doctor of Philosophy\par}
%       \bigskip
%       {\normalsize\bf \@title \par}
%       \medskip
%       {\normalsize by \authornames \par}
        \bigskip
    \end{center}
}
{
    \vfil\vfil\vfil\null    
\cleardoublepage
}
\addtocounter{secnumdepth}{1}
\setcounter{tocdepth}{6}
\newcounter{dummy}
\newcommand\addtotoc[1]{
    \refstepcounter{dummy}
    \addcontentsline{toc}{chapter}{#1}}
\renewcommand\tableofcontents{
    \btypeout{Table of Contents}
    \begin{spacing}{1}{
            \setlength{\parskip}{1pt}
            \if@twocolumn
            \@restonecoltrue\onecolumn
            \else
            \@restonecolfalse
            \fi
            \chapter*{\contentsname
                \@mkboth{
                    \MakeUppercase\contentsname}{\MakeUppercase\contentsname}}
            \@starttoc{toc}
            \if@restonecol\twocolumn\fi
            \cleardoublepage
    }\end{spacing}
}
\renewcommand\listoffigures{
    \btypeout{List of Figures}
    \addtotoc{List of Figures}
    \begin{spacing}{1}{
            \setlength{\parskip}{1pt}
            \if@twocolumn
            \@restonecoltrue\onecolumn
            \else
            \@restonecolfalse
            \fi
            \chapter*{\listfigurename
                \@mkboth{\MakeUppercase\listfigurename}
                {\MakeUppercase\listfigurename}}
            \@starttoc{lof}
            \if@restonecol\twocolumn\fi
            \cleardoublepage
    }\end{spacing}
}
\renewcommand\listoftables{
    \btypeout{List of Tables}
    \addtotoc{List of Tables}
    \begin{spacing}{1}{
            \setlength{\parskip}{1pt}
            \if@twocolumn
            \@restonecoltrue\onecolumn
            \else
            \@restonecolfalse
            \fi
            \chapter*{\listtablename
                \@mkboth{
                    \MakeUppercase\listtablename}{\MakeUppercase\listtablename}}
            \@starttoc{lot}
            \if@restonecol\twocolumn\fi
            \cleardoublepage
    }\end{spacing}
}
\newcommand\listsymbolname{Abbreviations}
\usepackage{longtable}
\newcommand\listofsymbols[2]{
    \btypeout{\listsymbolname}
    \addtotoc{\listsymbolname}
    \chapter*{\listsymbolname
        \@mkboth{
            \MakeUppercase\listsymbolname}{\MakeUppercase\listsymbolname}}
    \begin{longtable}[c]{#1}#2\end{longtable}\par
    \cleardoublepage
}
\newcommand\listconstants{Constants}
\usepackage{longtable}
\newcommand\listofconstants[2]{
    \btypeout{\listconstants}
    \addtotoc{\listconstants}
    \chapter*{\listconstants
        \@mkboth{
            \MakeUppercase\listconstants}{\MakeUppercase\listconstants}}
    \begin{longtable}[c]{#1}#2\end{longtable}\par
    \cleardoublepage
}
\newcommand\listnomenclature{Symbols}
\usepackage{longtable}
\newcommand\listofnomenclature[2]{
    \btypeout{\listnomenclature}
    \addtotoc{\listnomenclature}
    \chapter*{\listnomenclature
        \@mkboth{
            \MakeUppercase\listnomenclature}{\MakeUppercase\listnomenclature}}
    \begin{longtable}[c]{#1}#2\end{longtable}\par
    \cleardoublepage
}
\newcommand\acknowledgements[1]{
    \btypeout{Acknowledgements}
    \addtotoc{Acknowledgements}
    \thispagestyle{plain}
    \begin{center}{\huge{\textit{Acknowledgements}} \par}\end{center}
    {\normalsize #1}
    \vfil\vfil\null
    
}
\newcommand\dedicatory[1]{
    \btypeout{Dedicatory}
    \thispagestyle{plain}
    \null\vfil
    \vskip 60\p@
    \begin{center}{\Large \sl #1}\end{center}
    \vfil\null
    \cleardoublepage
}
\renewcommand\backmatter{
    \if@openright
    \cleardoublepage
    \else
    \clearpage
    \fi
    \addtotoc{\bibname}
    \btypeout{\bibname}
    \@mainmatterfalse}
\endinput
%%
%% End of file `Thesis.cls'.

Answer 1

As I already mentioned in comments, you want

\pagestyle{empty} 

on the pages where you want to get rid of the page number (here I guess the pages containing the abstract).

% Set up the document
\documentclass[a4paper, 11pt, oneside]{Thesis}  % Use the "Thesis" style, based on the ECS Thesis style by Steve Gunn
%
% Put your figures in this directory
\graphicspath{Figures/}  % Location of the graphics files (set up for graphics to be in PDF format)
%

% Include any extra LaTeX packages required
\usepackage[square, numbers, comma, sort&compress]{natbib}  % Use the "Natbib" style for the references in the Bibliography
\usepackage{verbatim}  % Needed for the "comment" environment to make LaTeX comments
\hypersetup{urlcolor=blue, colorlinks=true}  % Colours hyperlinks in blue, but this can be distracting if there are many links.

%% ----------------------------------------------------------------
\begin{document}
\frontmatter      % Begin Roman style (i, ii, iii, iv...) page numbering

%
\UNIVERSITY{{THE UNIVERSITY OF MELBOURNE }}    
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Update your department and school here:
\department{{Department of Mad Science}}
\school{{Melbourne School of Awesome}}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Set up the Title Page
% Change your thesis title and your information here
\title  {Thesis Title}
\authors  {\texorpdfstring
            {\href{your web site or email address}{Author Name\\ \small ORCID: }}
            {Author Name}
            }
\addresses  {\groupname\\\deptname\\\univname}  % Do not change this here, instead these must be set in the "Thesis.cls" file, please look through it instead
\date       {\today}
\subject    {}
\keywords   {}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\maketitle
%% ----------------------------------------------------------------

\setstretch{1.3}  % It is better to have smaller font and larger line spacing than the other way round

% Define the page headers using the FancyHdr package and set up for one-sided printing
\fancyhead{}  % Clears all page headers and footers
\rhead{\thepage}  % Sets the right side header to show the page number
\lhead{}  % Clears the left side page header

\pagestyle{fancy}  % Finally, use the "fancy" page style to implement the FancyHdr headers

%% ----------------------------------------------------------------
% The Abstract Page
\clearpage  % Abstract ended, start a new page
\pagestyle{empty}
bla bla 
%% ----------------------------------------------------------------
% Declaration Page required for the Thesis, your institution may give you a different text to place here
\clearpage  % Declaration ended, now start a new page

%% ----------------------------------------------------------------
% Preface Page required for the Thesis, your institution may give you a different text to place here
\clearpage  % Preface ended, now start a new page

%% ----------------------------------------------------------------
% The Acknowledgements page, for thanking everyone
\setstretch{1.3}  % Reset the line-spacing to 1.3 for body text (if it has changed)
\clearpage  % End of the Acknowledgements
%% ----------------------------------------------------------------

\pagestyle{fancy}  %The page style headers have been "empty" all this time, now use the "fancy" headers as defined before to bring them back


%% ----------------------------------------------------------------
\lhead{\emph{Contents}}  % Set the left side page header to "Contents"
\tableofcontents  % Write out the Table of Contents

%% ----------------------------------------------------------------
\lhead{\emph{List of Figures}}  % Set the left side page header to "List if Figures"
\listoffigures  % Write out the List of Figures

%% ----------------------------------------------------------------
\lhead{\emph{List of Tables}}  % Set the left side page header to "List of Tables"
\listoftables  % Write out the List of Tables

%% ----------------------------------------------------------------
\setstretch{1.5}  % Set the line spacing to 1.5, this makes the following tables easier to read
\clearpage  % Start a new page
\lhead{\emph{Abbreviations}}  % Set the left side page header to "Abbreviations"
\listofsymbols{ll}  % Include a list of Abbreviations (a table of two columns)
{
% \textbf{Acronym} & \textbf{W}hat (it) \textbf{S}tands \textbf{F}or \\
\textbf{LAH} & \textbf{L}ist \textbf{A}bbreviations \textbf{H}ere \\

}

%% ----------------------------------------------------------------
\clearpage  % Start a new page
\lhead{\emph{Constants}}  % Set the left side page header to "Physical Constants"
\listofconstants{lrcl}  % Include a list of Physical Constants (a four column table)
{
% Constant Name & Symbol & = & Constant Value (with units) \\
Speed of Light & $c$ & $=$ & $2.997\ 924\ 58\times10^{8}\ \mbox{ms}^{-\mbox{s}}$ (exact)\\

}

%% ----------------------------------------------------------------
\clearpage  %Start a new page
\lhead{\emph{Symbols}}  % Set the left side page header to "Symbols"
\listofnomenclature{lll}  % Include a list of Symbols (a three column table)
{
% symbol & name & unit \\
$a$ & distance & m \\
$P$ & power & W (Js$^{-1}$) \\
& & \\ % Gap to separate the Roman symbols from the Greek
$\omega$ & angular frequency & rads$^{-1}$ \\
}
%% ----------------------------------------------------------------
% End of the pre-able, contents and lists of things


%% ----------------------------------------------------------------
\mainmatter   % Begin normal, numeric (1,2,3...) page numbering
\pagestyle{fancy}  % Return the page headers back to the "fancy" style

% Include the chapters of the thesis, as separate files
% Just uncomment the lines as you write the chapters


%\input{Chapters/Chapter2} % Background Theory 

%\input{Chapters/Chapter3} % Experimental Setup

%\input{Chapters/Chapter4} % Experiment 1

%\input{Chapters/Chapter5} % Experiment 2

%\input{Chapters/Chapter6} % Results and Discussion

%\input{Chapters/Chapter7} % Conclusion

%% ----------------------------------------------------------------
% Now begin the Appendices, including them as separate files

\addtocontents{toc}{\vspace{2em}} % Add a gap in the Contents, for aesthetics

\appendix % Cue to tell LaTeX that the following 'chapters' are Appendices


%\input{Appendices/AppendixB} % Appendix Title

%\input{Appendices/AppendixC} % Appendix Title

\addtocontents{toc}{\vspace{2em}}  % Add a gap in the Contents, for aesthetics
\backmatter

\chapter{Tst}

%% ----------------------------------------------------------------
\label{Bibliography}
\lhead{\emph{Bibliography}}  % Change the left side page header to "Bibliography"
\bibliographystyle{unsrtnat}  % Use the "unsrtnat" BibTeX style for formatting the Bibliography
\bibliography{Bibliography}  % The references (bibliography) information are stored in the file named "Bibliography.bib"

\end{document}  % The End

NB: By the way, avoid links to overleaf, you should try to write a self-contained MWE (Minimal Working Example) in the post if you want to maximize your chances to get an answer (not all people here will want to create an account on overleaf, log in…). Here, your overleaf links breaks all notions of a MWE:

• it is not minimal (10 files are certainly not needed): writing a minimal example not only save the time of people that will help you, it also helps you to find exactly the line that is an issue.
• it is not working : after the title page, I see no roman numbers: