Can you post photos of your current TV settings? If you disable and re-enable Viera Link, does it change anything? What happens if you disable eARC?

I'll post some pics of the settings when I'm back home later.  The sonos app itself couldn't complete the TV setup, it kept failing to establish the viera link, so I would endlessly go through the cycle of being prompted to check the hdmi cable is connected to the eARC port, then saying 'still not visible" reconnect, retry and then the app would hang whilst trying to search for the TV. Essentially I can't turn on or off the viera link. 

If I disable eARC in the panasonic setup menu, then turn it back on, nothing changes. It's frustrating as I briefly had the mythical dolby atmos logo appear in the sonos app last night whilst watching via Netflix. Then this morning no sound at all. Disconnected, powered down, reconnected and powered up, got sound but no atmos even though the TV says dolby atmos being played. Sonos says no

Thanks for trying to resolve this matter 

This is the system info when the TV says its output is dolby atmos.. there seems to be an issue with the TV passing through the atmos to the arc via eARC. Any one else having this problem?

Are you using the HDMI cable supplied with the Arc, or an equivalent alternative that supports Atmos?

Hi.  I think @GuitarSuperstar was more interested in seeing your TV audio settings - can you post photos of those?

I'm using the hdmi cable as supplied with the Sonos Arc

And now, to.really annoy me, I have dolby atmos via the xbox. I just don't understand it.  I switch to Netflix on the TV app and I have no sound at all now. Confused

First, I can only assume that my earlier post was marked as best answer by mistake.

The most likely answer lies in the TV audio settings.  But nobody can help there if we can’t see what they are.

Sorry, busy day. The photo I took were way to large to be posted on the forum so I'll retake them at a lower resolution so they can be posted. 

When I try and run the setup for the TV via the sonos app, it keeps telling me to connect the hdmi cable to the eARC terminal. It most definitely is already in the correct port, but I unplug it,.reconnect it and the apps says it fails to establish viera link.  

Disconnect the Arc and all other devices from the TV. Unplug the Arc and TV from power for about a minute. Plug the Arc and TV back into power but leave everything disconnected. Be sure Viera Link is enabled, then run the TV Setup process in the Sonos app. Connect the Arc to the TV’s eARC port when the app instructs you to. When the TV Setup process is complete, test a Dolby Atmos source. If it works, connect your other devices to your TV and test again.

Thank you so much.... its only gone and done it. 

Really appreciate the help and knowing the order I which to connect all the various devices is really helpful. Thanks again. 

And then it stopped.  Swapped to my xbox one s, started an atmos app, the TV switched itself off then back on and it went back to 5.1  Is the xbox connection on hdmi3 causing the problem?

Yes, the Xbox is probably causing the problem. Try disabling CEC on the Xbox:

This feature can be turned on and off via the TV & A/V power options settings screen. Press the Xbox button  to open the guide, then go to Profile & system > Settings > General > Power mode & startup > TV & A/V power options.

You can also try connecting the Xbox to a different HDMI port or trying a different HDMI cable with the Xbox.

I've gone through the set up procedure again and I'm back to having dolby atmos via Netflix.

I'll definitely try a new cable. I've left the xbox unconnected for now until I have time to take everything apart and change the hdmi cable as access isn't easy. Plus I'll try a different hdmi port and see if that helps. One change at a time though and see what results I get. 

Cheers