sonos arc ultra stopped working

Disconnect the Arc Ultra from the TV and redo the TV Setup process in the Sonos app.

Is this something I’ll have to do often? Seems somewhat annoying 

You shouldn’t have to. But Samsung TVs are known to have issues.

Do you have any other devices connected to the TV?

I am also having this issue. I have had the arc ultra for under a week and have had to reset it up 3 or 4 times now as the speaker just no longer exists in the app. As soon as I have the app look for new products it finds it but it’s annoying to go through the setup process each time. It’s has great sound when it works. 

Are you also using a Samsung TV? If so, if you disable HDMI-eARC Mode on the TV, does it make any difference?

I have a very similar problem. At first, I tried to disconnect every device from my home theatre setup, but that did not help. Restarting Hi-Sense projector, Apple TV, Sub, Era 300 did not work either.

Since then, I realized that I have to power off the Sonos Arc ultra and power it back on. This fixed the problem every time. Strangely, that issue did not happen with my Sonos Arc SL, both on my TV or my Hi-Sense projector. 

I believe this is a bug with the Sonos Arc Ultra. Without powering the soundbar off and on, I seldomly lose Dolby Atmos, and then everything works in PCM2.0 even though Apple TV and projectors are properly configured (passthrough, eARC).

Basically now it hasn’t completely lost its settings in a week.  The main bug I am experiencing now is that if the apple TV goes to sleep or plays the screensaver, it forgets volume and everything is silent.  I can back in and out of apps on the apple tv for a minute or two and it picks back up the sound but it is always reset at zero volume.  I am going to see if setting the apple tv to never sleep helps keep it from forgetting. 

​@Delay I also experience this as well. It is pretty annoying, and again just on the Arc ultra. I start a movie, back out, go into Netflix again, and then the volume is back.

In a nutshell:

1. If I lose Atmos => power off and on the Arc Ultra
2. If I lose volume => leave the app on Apple TV, going in the app again, resume playing

Both happens when everything goes on sleep.

There could be multiple issues. 

First, disconnect all HDMI cables from the TV and power down the TV and soundbar for at least two minutes. Next, allow the TV and soundbar to reboot, but wait until the reboots complete before connecting the soundbar HDMI. Finally, reconnect other HDMI cables, if any.

Now we may need to deal with the nasty part. In addition to audio and video on the HDMI connection, there is CEC (Consumer Electronic Control). While the CEC goals are admirable, the details are poorly standardized. The goal is that the operator simply drops a disc into a player and all of the appropriate devices power up and select inputs. My favorite little glitch is the early morning cable box update. As a user convenience the final step of the update is to turn the cable box power ON. Unfortunately, CEC interprets this as a user request to watch TV and the user is awakened.

I suggest that you insert a CEC blocker in the AppleTV HDMI connection. This will prevent the AppleTV from attempting to dominate the CEC. Because the AppleTV CEC is blocked you’ll manually need to select it, but this is a small price to pay for system stability. You’ll also need to fuss with how the AppleTV remote sends Volume commands to the soundbar.

Thanks I will give the CEC blocker a try and report back.  I did try disabling the screensaver on the apple tv, I don’t know if that would prevent it from sleeping though and that didn’t work... still no sound on resuming.