Not sure if this will be your problem, but I had an issue where some usages of it tried to create temp files in /tmp, and somehow the permissions on the executable didn’t allow it to write there. Changed what it used for its temp folder, and all was well.
Often just installing the package you have linked is not enough, additional dependencies need to be installed too. The first thing you should do is try using the wkhtmltopdf binary directly and make sure is runs without error.
If you aren’t allow to install stuff on your hosting then you are better off using a PHP based engine like dompdf instead.
After a few attempts, I ended up giving up. I appreciate the suggestion of DomPDF, but unfortunately it does not have the resources that I need and that I only found in wkhtml