Regenerate Thumbnails in Wordpress

I wanted to ask a question here,
I had a problem with my server and I was able to resolve it only through backup. I use Ubuntu 22, OpenLiteSpeed, and CyberPanel.
Yesterday I installed two plugins on my website to recreate my Thumbnails:
  • Regenerate Thumbnails
  • Disable Generate Thumbnails
When I clicked on generate thumbnails of all images, a message like this came up:
“Unable to collect the list of attachment IDs via the WordPress REST API. You can check your browser console for details.”
After that, I gave F5, and that standard LiteSpeed 403 and 404 error page came up. I could no longer access my website. However, the others on the same account were normal.
How to resolve this if it happens again?

Second question)
The WebP Express Settings plugin, how to resolve this item too?
It seems your server setup does not support headers in .htaccess. You should either fix this (install mod_headers) or deactivate the "Enable direct redirection to existing converted images?" option. Otherwise the Vary:Accept header will not be added and this can result in problems for users behind proxy servers (ie used in larger companies)