Numbering in appendix

Question

When compiling my file, the appendices are not numbered (the sections are though, but they are counting throughout the appendices). Therefore it seems that the chapters are not recognized. In the appendices I use \chapter, \section and \subsection for the headers. Here you can find my code:

\input{Style} %in the preamble the \usepackage[titletoc]{appendix} is used

\begin{document}

\frontmatter
    \input{...}

\tableofcontents
\pdfbookmark[-1]{Contents}{Contents}

\mainmatter
\ChapterInsidePart
    \input{...} 
    \input{...}
    \input{...}

\backmatter
\input{...}

\appendix
\appendixpage
\addappheadtotoc
\renewcommand{\chaptername}{Appendix} %I added these lines of code to try and work around the problem. This would not help. 
\setcounter{chapter}{0}
\renewcommand{\thechapter}{\Alph{chapter}}
\renewcommand{\thesection}{\thechapter.\arabic{section}}
\setcounter{figure}{0} 
\renewcommand\thefigure{\thesection.\arabic{figure}}     
\setcounter{table}{0} 
\renewcommand\thetable{\thesection.\arabic{table}} 
    \input{...}
    \input{...}
    \input{...}
    \input{...}
    \input{...}
\underline{}
\end{document}

Answer 1

It seems to be a memoir document. Drop \backmatter, I do not see any reason to use it. It switches off the numbering.