The todonotes
list of todos appears empty when using the acl2020
style package (available here).
Here's a working example:
\documentclass[11pt,a4paper]{article} %list of todos is empty
\usepackage[hyperref]{acl2020}
\usepackage{todonotes}
\begin{document}
\listoftodos
\section{Contents}
test text \todo{test}
\end{document}
There's a similar question with the llncs
document style, however the fix, \setcounter{tocdepth}{1}
doesn't help.