Time Machine backup encryption password incorrect - where is the hint?

I recently removed the backup disk from Time Machine and attempting to add it again. It's a WD MyCloud plugged into my network. I can access the drive, but when I add again and select "Use Existing Backup" it ask for the Encryption Password, I can't recall the password and have exhausted all options. I looked in Keychain/Password app, which shows the laptop/system password, but that doesn't work. Is there any other means to get the hint? Entering multiple wrong answer does not trigger a hint.