Plesk login page displays error: DB query failed: Unknown error

Download the PowerShell script to a Windows server.

Unzip the file.

Right-click on the file "plesk178-admin-pass-reset.ps1" and click "Run with PowerShell" to run the script.

Create the psa_root user with a random password to perform further operations. Normally, this step is not necessary, since it is supposed to be executed during Plesk installation:

C:> plesk sbin mysqlmng_adm --inject-root

Remove existing admin user from Plesk SQL:

C:> plesk sbin mysqlmng_adm --del-user --user-login=admin

Create new admin user with random password:

C:> plesk sbin mysqlmng_adm --add-super-user --login=admin --password=new_password --allowed-host=localhost

C:> plesk sbin psadb -u --password=new_password

Note: in the commands above replace new_password with the required password