Please be optimistic. This is what I do for a living. I'm not guessing, I have done this a few times...
Apple TV can be plugged into your TV as well. It works the same way, but if you want it to go through Denon, we can do that too.
Plug it into Media Player on Denon. Switch to the Media Player input on Denon, and tell me if you get audio, video, both, or none. There may be some setup required, but I can walk you through that, so please leave it in the Media Player input.
For the PS4, there is a KNOWN issue of the video cutting out. It's due to the resolutions not being true movie or TV resolutions. They are graphics, and go slightly off the path, causing the picture to go black. It's best if you plug it into your TV, let the TV do its job of giving you a great picture, then running the audio from the optical out to Denon to let Denon do its job of surround sound. Notice how the sound on a TV isn't built very well on any TV these days? It's because they concentrate on the picture. Same goes for receivers, but they concentrate on audio.