I am currently hunting for errors in my template and these two I cannot solve after reading the log and researching:
First:
! Argument of \strip@prefix has an extra }.
<inserted text>
\par
l.60 postheadspace=\newline]{mystyle}
Second:
! Paragraph ended before \strip@prefix was complete.
<to be read again>
\par
l.60 postheadspace=\newline]{mystyle}
Minimal example:
\documentclass[a4paper, 12pt, oneside]{book}
\usepackage{amsthm}
\usepackage[unq]{unique}
\usepackage{thmtools}
\declaretheoremstyle[
numbered=unless unique,
%within=chapter,
headpunct={},
shaded,
spacebelow=\parsep,
spaceabove=\parsep,
notefont=\normalfont\itshape,
bodyfont=\itshape,
postheadspace=\newline]{mystyle}
\declaretheorem[
style=mystyle,
name=Theorem,
refname={theorem,theorems},
Refname={Theorem,Theorems}
]{FF}
\usepackage{hyperref}
\usepackage{cleveref}
\crefname{FF}{Theorem}{Theorems}
\Crefname{FF}{Theorem}{Theorems}
\begin{document}
\begin{FF}\label{ff1}
Test
\end{FF}
Link to \Cref{ff1}.
\begin{FF}\label{ff2}
Test2
\end{FF}
\end{document}