If you send me a private message ("PM" button below this text) with your registration code and the email address you sent the messages from, I'll get in touch with GPSoftware to see if they can find the messages.
Don't put those details in a public reply, of course!
Could be some anti-spam filtering or something. Seems odd for the online form to not recognise your code, though.
Do you know where the code was purchased from? GPSoftware themselves or another site?
Did you install the registration file after purchasing it? When the Licence Manager appears what "Type" does it say the licence is? By the sound of it it thinks you're using a Stock or Evaluation licence (as they're the only kind which will expire).
BTW, if you use Zone Alarm it can get in the way of installing the licence.