I have a latex file "main.tex" as follows:
\documentclass[alpha-refs]{wiley-article}
\usepackage{siunitx}
\usepackage{natbib}
\begin{document}
\section{Document class options}
\citep{urmson2008autonomous,lees2010theoretical} and \citep{geiger2012we}.
\bibliography{sample}
\end{document}
When I compile this via the terminal as pdflatex main.tex
It doesn't recognise the citations and does not produce a reference list:

The natbib error messages are:
Package natbib Warning: Citation `urmson2008autonomous' on page 1 undefined on
input line 10.
Package natbib Warning: Citation `lees2010theoretical' on page 1 undefined on i
nput line 10.
Package natbib Warning: Citation `geiger2012we' on page 1 undefined on input li
ne 10.
I haven't included the bib file sample.bib, because it does this with all references regardless.
pdflatex version:
pdflatex --version -> MiKTeX-pdfTeX 4.6.1 (MiKTeX 21.6)
Obviously, to compile the wiley-article.cls is needed. I have:
% wiley-article.cls, v1.5, 2018/07/05
% Developed by Overleaf.
Thank you!