Did you ever get a solution to your problem? I'm having the same problem and the other two replies in this thread weren't terribly helpful. Having paid for the thing, I'd quite like it to do what it's supposed to do. Quite apart from map updates, I'd just like to register the device to access any benefits and extra products that registration brings.
I had that problem. Got in touch with Navigon [not Garmin]. And got their phone number. Man guided me through steps. Think it meant deleting the memory within the Maps and More Unit and reinstalling the memory from the link he gave me. Took about 4 hours to do. Then take it to car and it links to your particular vehicle. Then reconnect it to PC and it then registered and downloaded necessary updates. He took me step by step to the download stage so I couldn't make any mistakes. Sorry I cannot remember the exact details.