I am in the same situation. Mid October 2015 and still their cellular is down. After spending an hour with this 1st level tech on the phone who did not know what is going on. He made me reboot as well as reset the touch screen. Later he transfered me to a different department. I explained them that I am getting full 4 green bars out of 5 but the connectivity test fails. The tech said they are not responsible for this and don't gurantee the cell connection. I told him at the time we signed up for xfinity home we were sold on that xfinity is giving a backup cellular system in case broadboand goes down. But he kept on saying that comcast is not responsible for cellular connection and there is no further support on this issue.
Shame on you Comcast/Xfinity.
