The access to an Avira account is denied if the login information is not correct. You can access your account directly via the Avira product without entering the login information and update your email address and password.
Note
Once logged in, click the triangle icon in the top right corner next to your name. In the drop-down menu click My account → Security and update your password.
If your Avira account is no longer linked to the product, try to request a new password.