! Incomplete \iffalse; all text was ignored after line 22. In \IEEEauthorblockN

Question

I get the error

! Incomplete \iffalse; all text was ignored after line 22. In \IEEEauthorblockN

Here's a MWE

\documentclass[conference,10pt]{IEEEtran}
\usepackage[affil-it]{authblk} 

\begin{document}
\title{ABC}

\author{\IEEEauthorblockN{Michael Shell\IEEEauthorrefmark{1},
Homer Simpson\IEEEauthorrefmark{2},
James Kirk\IEEEauthorrefmark{3}, 
Montgomery Scott\IEEEauthorrefmark{3} and
Eldon Tyrell\IEEEauthorrefmark{4}}
\IEEEauthorblockA{\IEEEauthorrefmark{1}School of Electrical and Computer Engineering\\
Georgia Institute of Technology,
Atlanta, Georgia 30332--0250\\ Email: see http://www.michaelshell.org/contact.html}
\IEEEauthorblockA{\IEEEauthorrefmark{2}Twentieth Century Fox, Springfield, USA\\
Email: homer@thesimpsons.com}
\IEEEauthorblockA{\IEEEauthorrefmark{3}Starfleet Academy, San Francisco, California 96678-2391\\
Telephone: (800) 555--1212, Fax: (888) 555--1212}
\IEEEauthorblockA{\IEEEauthorrefmark{4}Tyrell Inc., 123 Replicant Street, Los Angeles, California 90210--4321}}
\end{document}

Answer 1

The author block functionality is built-in to the IEEETran class. You do not need to include \usepackage{authblk}. (Commenting out this one line will allow your code to compile, though it does not print anything to output file as you haven't given the \maketitle command yet.)

\documentclass[conference,10pt]{IEEEtran}

\begin{document}
\title{ABC}

\author{\IEEEauthorblockN{Michael Shell\IEEEauthorrefmark{1},
Homer Simpson\IEEEauthorrefmark{2},
James Kirk\IEEEauthorrefmark{3}, 
Montgomery Scott\IEEEauthorrefmark{3} and
Eldon Tyrell\IEEEauthorrefmark{4}}
\IEEEauthorblockA{\IEEEauthorrefmark{1}School of Electrical and Computer Engineering\\
Georgia Institute of Technology,
Atlanta, Georgia 30332--0250\\ Email: see http://www.michaelshell.org/contact.html}
\IEEEauthorblockA{\IEEEauthorrefmark{2}Twentieth Century Fox, Springfield, USA\\
Email: homer@thesimpsons.com}
\IEEEauthorblockA{\IEEEauthorrefmark{3}Starfleet Academy, San Francisco, California 96678-2391\\
Telephone: (800) 555--1212, Fax: (888) 555--1212}
\IEEEauthorblockA{\IEEEauthorrefmark{4}Tyrell Inc., 123 Replicant Street, Los Angeles, California 90210--4321}}

\maketitle

\end{document}

gives:

If you have fewer affiliations, you can use the more traditional block form that has multiple columns:

\documentclass[conference,10pt]{IEEEtran}

\begin{document}
\title{ABC}

\author{\IEEEauthorblockN{Michael Shell}
\IEEEauthorblockA{School of Electrical and Computer Engineering\\
Georgia Institute of Technology,
Atlanta, Georgia 30332--0250\\ Email: see http://www.michaelshell.org/contact.html}
\and
\IEEEauthorblockN{Homer Simpson}
\IEEEauthorblockA{Twentieth Century Fox, Springfield, USA\\
Email: homer@thesimpsons.com}
}

\maketitle

\end{document}

which gives:

More information can be found on page 5 of How to Use the IEEETran LaTeX Class.