Hello
Operating system Debian 9.13
Mariadb:10.3.24
Plesk: 18.0.30 last update included
I found this entry in the logfile:
Trying to upgrade phpMyAdmin (files stage)... 'phpmyadmin' DB or 'phpmyadmin' DB user already exists, so phpMyAdmin configuration storage cannot be created. To create it, drop the respective DB and user, then run 'plesk repair installation' or reinstall the package.
This happened during upgrade from previous configuration storage, which was not removed: 'phpmyadmin_1HU90hTilWDF' DB and 'pma_1HU90hTilWDF' DB user.
Previous phpMyAdmin config was also preserved at /opt/psa/tmp/phpMyAdmin.config.php.save.
if I interpret this correctly, this entry must/should be deleted in the DB.
Note:
had this problem too, but I restarted the server and it worked again.