If the recovery code does not work, it is likely that you are using the wrong recovery code.

Zivver recovery codes are linked to specific passwords, not to user accounts. If you request a recovery code after changing your password, the recovery code will only work for messages sent or received after that password change. To restore access to your old messages, you need the recovery code corresponding to your old password. You received this recovery code on the date you created your account or set your password. Zivver shows you the date and time when you received the recovery code.

Follow the instructions on how to restore your messages carefully.