Warranty Registration Fails S33v3 modem

My new S33v3 modem works fine and is connected to Xfinity. When I try to register it with Arris for the warranty, when the online form validates the model, it tells me the serial number and model number do not match. I’ve tried entering the serial number multiple ways, same results. I verified the serial number through logging into the modem, as well as the tag on it. The registration screen tells me to call a phone number which is answered - no voice or message - then disconnects after a few seconds. If I try the online chat, it asks to check the warranty status first, which of course it fails because I am unable to register it. Any suggestions? Not feeling all warm and fuzzy at this point. Thanks.