I've successfully entered the serial number but this was linked to an old e-mail that I've no longer got access to (BT) . Whenever I try to make changes I'm directed back to support pages. Going round and round with no resolution.
Browse to the Magix website (magix.com) and log in to your account, Account icon is top right of the home page using the old email address and password, it does not matter if the email address no longer exists so long as you can remember the password.
Once logged in you can change the email address to your current one.
Contact Magix by email to infoservice@magix.net, giving them your serial numbers and order numbers email address you used. etc so they can reset your account email address password.