Set Debugging all the way up to highest - Developer.
That should display to your browser when you are attempting whatever.
On shared plans (cPanel/other panel?), normally there is an app for the web that will show only web service access logs and error logs. Look for it. On some shared hosting plans they have set up php to create a php error_log file in the directory where the error occurs. cPanel file browser and search for error_log might find. Then using cPanel file browser, view. Of course, you then have to interpret what it says ... or you could come back here and post clips of what it says (not that anyone would have a fix for ya).
However, having said that ... evidently where you host on shared plan is maxing out limitations/caps imposed by shared hosting. That's a guess.
Time to consider (if staying with hosting) or exploring option with hosting provider to move your site to either 'managed' (provider does heavy lifting and all you gotta do is ask) or 'un-managed' (you do the heavy lifting/config tweaks, etc.).
OR ... moving site to another provider that offers VPS leases ... read the fine print! :|
OR ... moving site to a Moodle Partner ... OR Moodle Cloud
https://moodle.com/moodlecloud/
If that is affordable and you are allowed to do what you want to do ... again ... read the fine print.
'SoS', Ken