I FIGURED IT OUT!!!! The Apple TV 4k turned on ULTRA HD Deep Color and the Cable Box is not compatible!!! OMG!!! If anyone else has this problem, now you know!!!
I'm running an ONKYO TX-RZ710 and all of the sudden, I am getting no sound from the CBL/SAT input when I watch cable. I tried different HDMI cables, I swapped cable boxes and nothing. I connected the cable box to the AUX input and I do get sound, so it's not the box or cables. I checked the settings on the (both) boxes and they are set to output digital. When I connect something else to CBL/SAT (blu-ray) I get sound. One time I saw a quick error message flash on the screen but it went away too fast for me to see what it said. When the cable box is connected the front display does not say HDMI, but when I connect the blu-ray it does. Is there a setting I'm missing? Did my 2 year old daughter press a button on the remote??? HELP!!!
UPDATE- I think it's a bad input. I started getting no picture or sound, so I swapped things around again and even with the blu-ray connected I'm still getting no picture or sound. I think that one time may have just been the input working one last time.
UPDATE 2- I called Onkyo and did some troubleshooting and we are both perplexed. Here is what was done...
Full reset to factory settings.
Swapped cable boxes.
Disconnected all devices except the one we are testing
Cable Box in CBL/SAT = Picture but NO SOUND
Cable Box in BD/DVD = Picture and sound
Blu-ray Player in CBL/SAT = Picture and sound
Blu-ray Player in BD/DVD = Picture and sound
Cable Box in PC = Picture and sound
Multiple HDMI cables used with the same result.
So the ONLY combination that doesn't work is Cable Box in CBL/SAT, which only stopped working 4 days ago and had been working for 7 months. The only thing that changed in all that time is I added APPLE TV to the receiver but in a different input.