Not exactly sure what happened, but the Netflix app on the 4th generation Apple TV (non 4K) stopped playing audio. I have a feeling there was an update to the Netflix app and the update is implementing digital copy protection. Maybe this could be related to the future inclusion of Dolby Atmos in the 4K version of the Apple TV???
I do have an external receiver connected to a sound bar and speakers. The Apple TV is connected to the TV via HDMI, and I use the optical out of the TV to feed the receiver. All this time, this setup has worked out. As an interim solution, I changed the sound settings of the Apple TV to stereo. It’s good enough for now, but I have a feeling more changes are coming when and if my AV setup is complete. My current (non-HDMI) Dolby surround receiver won’t be able to handle the protected signals so will eventually need replacing.
But I have read up on HDMI ARC (Audio Return Channel) to see if this will fix things.