Scenario: you made a password-protected backup and forgot the password.
Unfortunately there’s no solution other than finding the original password.
For reliable safety of user data, password-protected archives are encrypted with a 256-bit key based on the password. This makes them inaccessible without the original password. There’s no backdoor into this encryption. If you don’t have the original password, it’s not possible to extract data from this archive (within capabilities of modern computers).
When using password protection, always be careful and back up your password in a safe place.