Using titlesec package

I’m using a template provided by my university and I tried to change the format of the section titles using the titlesec package as follows

usepackage[explicit]{titlesec}

titleformat{section}{bfserieslarge}{arabic{section}. #1}{6pt}{}

However, the moment I implemented the title of my appendix suddenly disappeared from the PDF. I’m not sure what is going on. I’ve pasted the code for my main.tex file below in case the error might be present anywhere else.

documentclass[a4paper]{article}
usepackage[margin=1in, footskip=30pt]{geometry}

usepackage{amsmath}
usepackage{graphicx}
usepackage{hyperref}
usepackage{float}
usepackage{booktabs}
usepackage{tabu}
usepackage{subcaption}
usepackage[toc,page]{appendix}
usepackage{url}
usepackage{todonotes}
usepackage{fancyhdr}
usepackage{booktabs}
usepackage{multirow}
%usepackage{gensymb}
usepackage{caption}
usepackage[ruled,vlined]{algorithm2e}
usepackage{siunitx}
usepackage{systeme}
usepackage{enumitem}
usepackage{comment}
usepackage{braket}
usepackage[explicit]{titlesec}

titleformat{section}{bfserieslarge}{arabic{section}. #1}{6pt}{}

makeatletter
setlength{@fptop}{0pt}
makeatother
usepackage{natbib}
DeclareRobustCommand{gobblefive}[5]{}
newcommand*{SkipTocEntry}{addtocontents{toc}{gobblefive}}
setlist[itemize]{noitemsep, topsep=0pt}
renewenvironment{abstract}
 {
  begin{center}
  bfseries abstractnamevspace{-.2em}vspace{0pt}
  end{center}
  list{}{%
    setlength{leftmargin}{11mm}%
    setlength{rightmargin}{leftmargin}%
  }%
  itemrelax}
 {endlist}

begin{document}

setlength{parindent}{0em}
setlength{parskip}{0.75em}

input{Chapters/00Titlepage.tex}

thispagestyle{empty}
addtocontents{toc}{protectthispagestyle{empty}}
pagenumbering{gobble}
setlength{parskip}{11pt}
pagenumbering{arabic}

clearpageinput{Chapters/0Abstract.tex}
tableofcontents

clearpageinput{Chapters/1Introduction.tex}
input{Chapters/2Problem_Description.tex}
input{Chapters/3Theoretical_Model.tex}
input{Chapters/4Extended_Model.tex}
input{Chapters/4Model.tex}
input{Chapters/5Evaluation.tex}
input{Chapters/6Conclusion}


clearpagebibliography{bibliography.bib}
bibliographystyle{unsrt}

appendix
clearpageinput{Chapters/Appendix.tex}
clearpage
pagenumbering{Roman}

end{document}

Any help would be appreciated.