What can cause an WordPress Site to give a HTTP 500 error?

Here's an article that explains HTTP 500 errors and what you may be able to do about them - https://www.ionos.com/digitalguide/h...-server-error/

Likely a plugin conflict.

This is a pretty easy thing to figure out if so, once you've gone through the process one time. I learned to do it around 2014 and stopped needing 99% of host technical support as I could diagnose my own problems.

Go into your cpanel at your host, or find the equivalent (Siteground has their own replacement for cpanel now for example). Look for the File Manager or equivalent.

Find your website's files and look in the directory for the error log.

Open the error log as a text file and look at the last few log entries. They will probably tell you what the problem is.

Go into the wpcontent directory for the site plugins, and delete that plugin. Note you are not logging into your website to do this: you're doing it directly through the host.

See if that deletion fixes your problem by refreshing the domain url in your browser. If not, continue deleting plugins until the site works again. You can always reinstall plugins later after you're able to log back into the website.

If the error log turns out to be a hostile sql insertion or something like that, you need to talk to your host.

This is much simpler than all these words could make it seem. It's pretty easy once you know where to look.