After subscribing a new VPS server from my hosting provider, I found that although I could access to Plesk control panel properly, I was unable to access MySQL with the same admin’s user and password as used in Plesk. As a result, I couldn’t do anything with the database from the command line or in any other way. So I decided to manually change the admin user’s password via the mysql shell. After making such change I could perfectly log in to MySQL, but nevertheless the Plesk control panel stopped working, throwing the following exception:
ERROR: PleskFatalException – Unable to connect to database: saved admin password is incorrect.