I used all capital letters. I had the caps lock on. I don't know if I really got a response code or if it was a challenge code. Never done this thing. On the page where you enter the old registration number, it had some type of code at the bottom. Maybe that was the challenge code. After I entered the old serial number and hit the register key. I got a screen that said "Thanks for registering.' that lasted about one second and then I was told everything was wrong. Don't understand because this should be straight forward. Bill