I have an LG C3 TV, a Sonos Arc, and a Sonos Sub Gen 3. Earlier today I factory reset all of these devices and started from scratch. I started by connecting the Arc to the TV and using video/audio content from the TV itself (antenna or TV apps). In this situation everything works as expected (audio is being passed through to the Arc, and I can use the volume +/- and mute buttons on the TV remote to control the volume of the Arc.

I have two other HDMI devices that I would like to connect to the TV, a Samsung Blu Ray player, and an AppleTV 4k. As soon as I plug in the HDMI cable for either of these devices into the TV, I lose the ability to control the Sonos volume using the TV remote (or the other connected device remote).

For example: If I connect the AppleTV and use the volume controls on the Apple TV remote, I can see it “changing” the TV volume via the TV interface (which has no effect since sound is coming through the Arc), but the volume changes aren’t passed onto the Arc. The same is true if I just connect the BluRay player and use the Blu Ray player remote to try and change the volume. As soon as I disconnect all HDMI devices from the TV except for the Arc, the ability to control the Arc volume from the TV remote returns.

I’ve tried to simplify the configuration as much as possible here and am using the following TV settings:

HDMI Input Audio Format: Bitstream

Digital Sound Output: Pass Through

eARC Support: On

I just would like to have control of the Sonos Arc volume with an external device providing the video/audio to the TV. I welcome advice either on settings/troubleshooting to try, or about which device is most likely at fault. Since it seems to happen both with a Samsung Blu Ray player and the AppleTV 4k, it seems like either the TV or the Sonos Arc is failing to pass on/receive the volume change instructions.

Thank you!