I heard from CS. You can reset your TSB 20 password if you uninstall the game and reinstall it. From there when you sign in click “forgot password,” and you’ll be able to reset it then use it for TSB 21.
I have the same issue. I don’t even think I created a password in the first place. Additionally, what features carry over to the new version—do we keep our unused $, gold, XP points etc.?