I have had a problem like that with other products. What I ended up doing was to type it in.
You might check and make sure and numbers lock isn't on, and that caps are not locked in.
You could also request a registration number look-up just to re-verify that you are using the right number. It has been a long time since I registered something.... but when I did I remember I was trying the wrong number for some reason.
If nothing else works you can contact firstname.lastname@example.org. They are friendly folk.