How do I get "Appendix" to appear in each appendix section title?

Question

I am writing a document in Latex. I would like the word "Appendix" to appear in each section title. For example, the first section should be: "Appendix A: Proofs". Unfortunately, "Appendix" does not appear in the current titles: for example, the current title of the first section is just "A: Proofs".

Is there an easy way to fix this? Unfortunately, none of the solutions here worked (I have no idea why).

Here is a minimal(-ish) working example:

\documentclass[12pt]{article}
\usepackage{geometry,ulem,graphicx,caption,mathtools,natbib, xcolor,setspace,comment,pdflscape,array, parskip, booktabs, bbm, titlesec, lipsum, footmisc, color, amsthm, tikz, subfig}
\usepackage{footnotebackref}
\titleformat{\section}
  {\normalfont \scshape}{\thesection.}{0.5em}{}
\titleformat{name=\section,numberless}
  {\normalfont \scshape}{}{0em}{}
\usepackage[titletoc]{appendix}
\geometry{left=1.0in,right=1.0in,top=1.0in,bottom=1.0in}
\makeatletter
\renewcommand\hyper@natlinkbreak[2]{#1}
\makeatother
\begin{document}
\renewcommand{\appendixname}{}
\begin{appendices}
\textsc{Appendices.}
\section{Proofs}\label{app_sec_proofs}
\end{appendices}
\end{document}

Answer 1

IMHO this is an incompatibility of packages titlesec and appendix. Without titlesec it works. However, you can add a generic hook to change the \section formatting with titlesec, whenever environment appendices starts:

\documentclass[12pt]{article}
%\usepackage{geometry,ulem,graphicx,caption,mathtools,natbib,xcolor,setspace,comment,pdflscape,array, parskip,booktabs, bbm}
\usepackage{titlesec}% the only relevant package beside appendix
%\usepackage{ lipsum, footmisc, color, amsthm, tikz, subfig}
\usepackage{footnotebackref}
\titleformat{\section}
  {\normalfont \scshape}{\thesection.}{0.5em}{}
\titleformat{name=\section,numberless}
{\normalfont \scshape}{}{0em}{}
\AddToHook{env/appendices/begin}{%
  \titleformat{\section}
  {\normalfont \scshape}{\sectionname~\thesection.}{0.5em}{}
}
\usepackage[title,titletoc,page]{appendix}
\makeatletter
\renewcommand\hyper@natlinkbreak[2]{#1}
\makeatother
\begin{document}
\begin{appendices}
\textsc{Appendices.}
\section{Proofs}\label{app_sec_proofs}
\end{appendices}
\end{document}

or with : instead of . and option page instead of a handmade page title:

\documentclass[12pt]{article}
%\usepackage{geometry,ulem,graphicx,caption,mathtools,natbib,xcolor,setspace,comment,pdflscape,array, parskip,booktabs, bbm}
\usepackage{titlesec}% the only relevant package beside appendix
%\usepackage{ lipsum, footmisc, color, amsthm, tikz, subfig}
\usepackage{footnotebackref}
\titleformat{\section}
  {\normalfont \scshape}{\thesection.}{0.5em}{}
\titleformat{name=\section,numberless}
{\normalfont \scshape}{}{0em}{}
\AddToHook{env/appendices/begin}{%
  \titleformat{\section}
  {\normalfont \scshape}{\sectionname~\thesection:}{0.5em}{}
}
\usepackage[title,titletoc]{appendix}
\makeatletter
\renewcommand\hyper@natlinkbreak[2]{#1}
\makeatother
\begin{document}
\begin{appendices}
\section{Proofs}\label{app_sec_proofs}
\end{appendices}
\end{document}

Please note, redefining \appendixname to an empty string, does not make sense, if you want "Appendix" prefixes in the table of contents or the titles, because options title and titletoc uses exactly, this \appendixname. For this reason, I've removed your \renewcommand{\appendixname}{}.

If you want to change the title "Appendices" either in the ToC or of the appendices page, see \appendixtocname and \appendixpagename in the appendix user guide.

For an alternative suggestion using scrartcl instead of article and package appendix see, e.g., this answer.