This problem seems to be different but it comes while I've been having the problem previously reported at https://community.apachefriends.org/f/viewtopic.php?f=16&t=82729.
In this case the website went from working fine to receiving a response that says nothing but "Error Establishing Database Connection". There was nothing changed on the website in question but there are other websites that have been accessed that are installed on this same instance of XAMPP. Unlike the situation in the topic referred to above there has NOT been any changing between instances of XAMPP. However, this is XAMPP 7.4.33 which worked just fine on 3 different reinstalled websites the day before this problem arose. The only thing that happened between things seeming to work fine and this error is that both MySQL and Apache were stopped using the XAMPP Control Panel. The computer was shutdown overnight. When testing resumed the next day the problem appeared.
Notably the message says "Error Establishing Database Connection". However, there is nothing in the mysql.error.log file that suggests there was any contact with MySQL. At the same time there is no problem accessing MySQL when using phpmyadmin by accessing the localhost on the server machine. When doing that there is a message that gets displayed on the bottom of the screen as follows:
The phpMyAdmin configuration storage is not completely configured, some extended features have been deactivated. Find out why.
Or alternately go to 'Operations' tab of any database to set it up there.