I have no idea why the following MWE should have errors. I would really appreciate it if you could help.
\documentclass{article}
\usepackage{color,soul}
\begin{document}
\hl{used the Monte Carlo simulation to explore different staffing policies and minimize infections among SMs on non–COVID-19 wards. They reported that longer nursing shifts and less co-rotation of SMs (no more frequently than every three days) may lead to fewer infections.}
\end{document}