You have two options:
a. You are still logged in on a mobile device with biometrics:
If you are still logged in on your mobile device and have fingerprint, touch ID, or face ID activated you can set a new Master Password on your mobile without losing your data.
To do so, please go to Settings and select Change Master Password and follow the instructions.
b. You are not logged in on a mobile device:
As Avira does not know your Master Password and therefore does not have access to your data, there is no possibility to restore access. You have the option to reset your account and set a new Master Password, but this will erase all your existing data.
To do so, when prompted to enter the Master Password click the “reset account” link at the bottom and follow the instructions.