TV box "offline"

I have a pretty new (6 months old)  Xfinity Wifi Gateway XB6-T G95CGM414X Router in my home. Just this past week, when I tried to connect my new Smart TV to the internet to watch Hulu, I noticed that all of my TV boxes come up as "Offline". I thought this was a mdem/router in one...do I need a separate router or is it possible I am missing some hook-up with the modem that is causing the signal to not go out to the cable boxes? 

The cable boxes are fully functional otherwise. I get all of my TV channels, etc. It just seems like the internet is not going through to either of the new smart TVs we just purchased. 

Thank you in advance!