Board Thread:Support Requests - Community Management/@comment-24.20.18.80-20201019164149/@comment-168424-20201019174409

Assuming your email for the account is legit, depending on how long it has been since you tried to request a new password the problem could have been created by the FANDOM and Gamepedia account merger where some usernames were changed due to duplication. However, your email should still work, in theory.

Like TyA suggested, only FANDOM staff who have access to search the accounts DB can tell if your email is legit and then see how they can help you from there.