Are both TVs 4K? Did you try the working HDMI cable and box on the non-working TV? Is there a 4K setting on the input menu on the TV? Have you tried a working TV in the same location as the non-working tv, or the other way around?
I am having the exact same issue with a recently purchased HISENSE TV. Funny thing is it worked fine for a few months and then wireless box quit working on it yet works fine on other LG TV
My Vizio is two years old. I can not play Netflix and YouTube through the TV no problem. I can stream Netflix and YouTube to the TV and also to Chromecast plugged into the AVR with no signal issue. I think it’s on the Verizon side.
i just bought a new Samsung series 8 UHTV and have a similar issue. Everything works find with my old Samsung but with the new one, only works using the mini box using WiFi. If I use either the main set top box or mini box using the coaxial cable, the tv will not be able to find source. of course Fios blames Samsung and Samsung blaming Fios.
I had the same issue with a cheap SuperSonic TV. The two wouldn't connect unless I rebooted the mini. But if I turned the TV off and back on I'd have to reboot the mini again.
The solution for me was to change the mini's output from 1080p to 1080i.
That's it! Hope it helps someone out there.