Decentralized wallets are just that, decentralized. All user authentication content, such as transaction password, Private key, Mnemonic, etc. are stored on local devices (decentralized) not stored on the centralized servers. If you forget the password, there is no way to reset it through a third party agency (such as the imToken team).
The only way to reset the password is by re-importing the Mnemonic or Private key.
On that note, you want to make sure that the Mnemonic or Private key you backed up is correct.