Issue :
A MySQL database was created and still does exist but it is not being listed in the Plesk interface.
Solution :
This usually happens when the database is not created via Plesk. Instead, it might have been created via SSH.
To get around this, there are two ways :
1. This is the simpler of the two.
Just take a dump of the database.
mysqldump -u <username> -p <password> databasename > databasename.sql
Drop the database.
mysql -u <username> -p <password>
drop database <databasename>
Create the database via Plesk.
Plesk Control Panel >> Domains >> Mysql Database >> Add Database
Restore the database.
mysql databasename < databasename.sql
2. Another method is a bit complex one and is advised for expert users only.
After taking a backup of the current psa database, you will have to edit it from the backend and add the database details in the database table manually.