Thanks for joining the conversation, kellyntrapp! A serial number beginning with AGXH corresponds to the PIXMA iP8720 specifically meant for sale only in Canada. If you're trying to register it with Canon USA, it won't go through as our site is set up to only recognize US-model serial numbers.
If you live in Canada, be sure to register your product with our friends at Canon Canada. If you live here in the United States, then we recommend contacting your dealer to let them know that this product wasn't meant for sale in this country and to see what they might be able to do for you.
Hope this helps!
