Issue Plesk app malfunctioning since last update

[ivanes82]

Since the last update that allows changing the admin user name, the app has stopped working correctly. The lower buttons of the app are no longer visible. Reset the username to admin, it shows them again, but gives credentials error.

 

[Peter Debik]

A user name other than "admin" does not work with the app at this time. This is a known issue that will be fixed in some future update. Internal ID PMBL-652.
I have no specific steps to solve it in an existing app installation, so I believe you could try to remove and reinstall the app to fix it.