CM700 SERIAL Number different on isp

I setup the new modem with the ISP. Tried connected to the internet but couldn't get a down link. Looked on the ISP website and noticed the serial number had a 1 character difference from what is on the modem. Upon contacting the ISP, they stated the serial they had on file registered fine and they could see the modem on the network, but weren't receiving messages. They also said the corrected serial from the modem is a no go. Is this a common issue?