I called xfinity support, they changed something at their end and asked me to reset the network settings. I am able to receive the call now, hopefully it lasts.
Cool! great thing. Thanks for posting. Do you have any more details on what they changed? I did have the call failure initially a lot for almost all of the incoming calls but has since reduced a bit. I re-enabled the Cellular data, and rebooted. Not seeing that many "system failure" message but occassionally do.