5ghz band not working

I have the xfi router and have set up 2 different network names / passwords so that we can support devices that can only connect to the 2.4ghz band. Haven't had an issue for 3 months. As of this morning the 5ghz band no longer works. It shows up as a network but when trying to connect it either doesn't connect or if it does (after resetting) it works for about a minute before not working again.

I chatted with comcast - they merged the network and then somehow made it worse. Afterwards I called them and we broke them into 2 networks again worked for a minute and then didn't work after I got off the call with them. They say everything looks fine on their end.

Any help would be appreciated