sb8200 offline after power outage

My sb8200 has no connection (is offline) after a short power outage last night. I have a separate router and it says that the network cable is unplugged and it is not. I have restarted and manually restarted both the modem and the router, even leaving both unplugged completely overnight. I contacted xfinity and they cannot figure it out either. Does this mean I need a new Ethernet cable? I have also read that maybe I have to factory reset the modem but I am not sure what to do. We have only had this modem router combo for under a year I can’t imagine it is already toast.