Samsung Smart TV won't stay connected to xfi gateway

Recurring difficulties with Samsung Smart TV not staying connected to the xFi gateway - but TV connects to my phone when I used it as a hotspot. The modem is maybe 4 ft. away from the TV. Talked with Xfinity support several times, tossed it back to Samsung who tossed it back to Xfinity. Xfinity sent someone out to the house, they replaced the modem and I upped our plan and ordered a pod for the back office. Signal strength and speed is great now. The Samsung TV also connected fine to the new modem and stayed connected well until now. Same issues - the TV connects to a phone as a hotspot with no issues. Often after a reboot, it will say it is connected but I still can't open any apps and if I go back in to see the network status, it will say it's not connected then. I've done basic resetting on the modem and the Samsung TV. No resolution. Normally I would say that because this is the only device we're having issues with, it could be the device, and it might be, but as mentioned, the TV connects to a cell phone as a mobile hotspot without issue. Any insights would be helpful!