If you lost your Plesk Administrator Password, you can reset/see this with an SSH or Remotedesktop-Connection.

For Linux:

If you lost your password for your Parallels Plesk Control Panel. You can reset the password via SSH with an SSH client of your choice. When you are connected use this command:

Plesk Obsidian (18.x)

plesk login

Two links are generated. Use the second link based on the IP address to log in to Plesk as an administrator. For example:
https://10.52.43.73:8443/login?secret=uT%2BlFXgNQ2dnec3HBdMafGd7ZFoXrVA5jWLATap5smQ%3D

Reset your password by running this command:

plesk bin admin --set-password -passwd <new_password>

Plesk Onyx (17.x)

/usr/local/psa/bin/admin --get-login-link