After upgrading WordPress version to 5.02, in many websites has been problems with ”connecting database”. etc. One reason can be that in the site’s can be a different .config file than what server dashboard shows. This conflict may causes slowness, which leads connection errors.
Custom config is a hidden file like .ovhconfig.
To check if your php version is different in your website than in your host server, make a phpinfo.php file and put that file into your website’s root
/ using FileZilla for example.
// Show all information, defaults to INFO_ALL
// Show just the module information.
// phpinfo(8) yields identical results.
How to change your PHP version and upgrading to PHP 7
Restoring Your Database From Backup
How do I view my PHP environment settings?
How to deactivate all plugins when not able to access the administrative menus?