To fix the problem, you need to perform several actions:Thanks for your response. I've tried it several times and also read the troubleshooting article. However, the 'background-css' folder does not exist, and even after creating the folder and setting the permissions to 755, it is being deleted automatically after a while, leading to an error when updating posts or pages.
1. Deactivate and remove the WP Rocket plugin.
2. Remove all caching plugins incompatible with the WP Rocket plugin.
Disable caching in the Theme settings, if there is such a function.
3. Deactivate, at the time of troubleshooting, all protection plugins
((especially such as Anti-Hacker and so on).
4. Optimize and clean the Database with the Advanced Database Cleaner PRO plugin - you need to be able to use this plugin (before using it, make a backup of the Database). You need to remove all the remnants of previously installed plugins from the Database.
5. If all WordPress folders are not restored, you need to download it and reinstall it from the archive. If you can't do it yourself, contact the Hosting Support Service - they will help solve the problem.
6. After fixing the problem, install and activate the WP Rocket plugin.
Check his work.
7. Activate all disabled plugins (only necessary ones).