[OS X TeX] adding multiple authors

[Alireza Dehghani]

I am trying to use multiple authors with multiple affiliation using 
authblk package.  I 
think I am coding it right, but latex compiler is completely skipping 
the author block. 
Not giving any error either.  Any idea ? thanks. 
Here is what I wrote : 
\documentclass[12pt]{amsart}
\usepackage{hyphenat}
\usepackage{flafter}
\usepackage{txfonts}
\usepackage{cite, graphicx}
\usepackage{geometry}
\usepackage{anysize}
\usepackage{titlesec} 
\usepackage{amsmath, amsthm}
\usepackage{multirow}
\usepackage[square,super,comma,sort&compress]{natbib}
\usepackage{enumerate}
\usepackage{textcomp} 
\usepackage[version=3]{mhchem}
\usepackage{subfigure}
\usepackage{authblk}
\geometry{a4paper} 
\linespread{1.15} 
\marginsize{2.5cm}{2.5cm}{2.5cm}{2.5cm} 
\titlelabel{\thetitle.\quad}
\pagestyle{plain} 
\pagenumbering{arabic}
%\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
%Abstract
\renewcommand{\abstractname}{\textbf{\bf Abstract:}} 
\title{My Title}
\author[1]{author1}

\author[1]{author2} 

\author[2]{author3} 

\author[2]{author4} 

\affil[1]{affil1} 

\affil[2]{affil2 } 

\begin{document}

\maketitle
{\normalfont \bf Keywords:} keyword1; keyword2; keyword3.

\input{source/Introduction.tex}

\input{source/Experimental.tex}

\input{source/Discussion.tex}

\bibliographystyle{unsrt}
\bibliography{library}
\end{document}
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