I have exactly the same issue since end of January.
In contact with Pyur/TC since 2 weeks now...unbelievable.
I did all the required steps to have the new firmware on my new 6490.
Once I want to use the Aktivierungsportal I'm getting the silly notification.
Latest measure from Pyur/TC -> they will reset my login, which takes a couple of days and can only be done via DeutschePost...
...I don't blieve this will solve it, but seeing is believing.
Has anybody solved this lately or similar experience?