So, I tried navigating to an inexistent page on my website, for example, https://www.thevhgroup.ml/page.html and that page is showing me 500 Internal Server Error
I checked my .htaccess and it’s showing the updated error page URLs.
Just checked .htaccess again and found one error. In cPanel, I had used the full URL like: https://www.thevhgroup.ml/404.html and so, in .htacces, it was converted to http://https://www.thevhgroup.ml/404.html. I thought that was giving me the error and so, changed it to only https://www.thevhgroup.ml/404.html. Cleared cache and everything. Still getting the same 500 error page.
I checked your .htaccess file and it looks like there are still many old rules in there. For example, I see references to SitePro in there, which pretty much overrules your own 404 error pages.
Please clean up your .htaccess file so only the rules you need are in there, or just remove the file and reconfigure it from there.