You definitely what to get atmos over  PCM 5.1.   

Are you using your TVs smart app or an externally connected device, like AppleTV, Roku, FireTV, etc?  Is the setting you were referring to on the TV or someplace else?

Unfortunately, in order to get atmos working everything entire the chain needs to be set right.  Netflix (or whatever service you’re using) has to have the content in Atmos.  Netflix requires a premium tier service for this.  Then, the particular version of the netflix app has to be atmos compliant.  There are cases where a smart TV app doesn’t do Netflix.  Then your TV has to be set right, and some TVs won’t play atmos from their smart apps, but will pass it through from HDMI sources...or vice versa.

I haven’t used my Samsung TVs smart app in a while, but I believe I could not get the Netflix smart app to do atmos.  I can get it using my Nvidia Shield though.

Many Thanks dear Danny for you response.

I am using a 2021 samsung TV eARC compatible. 

Also using TV  build in Netflix app.

Few days ago, with the same TV , Netflix content like 6 underground or the old Guard were showing atmos in the sonos app, so I assume I was able to get Atmos.

I haven't changed anything ro my tv settings. But somehow same movies show dolby multichannel pcm 5.1 in sonos app. I am wondering if this is sonos app issue ?

My TV setting

- sounds output: receiver (HDMI)

- HDMI-eARC Mode: auto

- Digital output audio format: auto

- Dolby Atmos Compatibility: checked. 

With these settings , I was getting atmos to show in the app, but all of sudden I am now getting dolby multichannel pcm 5.1 

The Sonos app should not be a factor.  Hard to imagine you’re getting atmos, as you did before, but the app is reporting incorrectly.  The app is not involved in the transmission of the audio from your TV to Arc.

Did your TV get a firmware update recently?  Is there one available?    Anything change with your Netflix account?

I might try unplugging your  TV for a few seconds to give a cold reboot.  Maybe check with Samsung support if there were any issues.   You could try Sonos support, maybe do a diagnostic to verify what audio signal is coming to your Arc, but I would honestly do that last.  If there is an issue with Sonos playing atmos, we’d hear a lot more noise about it on these forums.

And of course, someone else on here may have some better advice...

This is a great question and one I would like to understand better.  I have my Arc, play1’s x2  and a sub hooked up to a Sony TV through eArc.  When I watch Netflix through Apple TV I get Stereo PCM.  If I watch through the native app I get Dolby digital+ or multichannel PCM.  I do get ATMOS through some sources, not Netflix,  so I know I have everything set up right.  My Netflix subscription is Standard HD.  Does this mean I need to upgrade to premium to get better audio quality with my Arc?  Thanks.

@JuniorT Do you have a Pass Through option for the Digital Output Audio Format setting on the TV? If you set it to this setting, what audio format does the Sonos app display when watching Dolby Atmos content from Netflix?

@jimroy You need a premium Netflix subscription to get Dolby Atmos audio. If you have an Apple TV 4K and want Dolby Atmos audio, your TV must be equipped with HDMI eARC. If your TV only has HDMI ARC, go to you the audio settings on the Apple TV and set Change Format to ON and set the Audio Format to Dolby Digital.

You need the premium plan with netflix in order to get any atmos content, last time I check.  I can’t imagine that’s changed.  Once you do that, you will likely need to close or rebooot the app on Apple TV or your native app.  That still isn’t a 100% guarantee as I don’t know if atmos is enabled on Apple TV and netflix app (I think so, but can’t confirm) or Sony TV Netflix smart app.  Probably will work, but it didn’t work for Samsung when I initially tried it about a year or so ago.

@GuitarSuperstar When watching netflix, passthrough option is greyed out,  so can't change it.

When I first installed my TV a month ago, the only think I did to get sonos app dispplaying atmos when watching atmos content from TV build in app was setting eARC on auto.

Now with the same settings , atmos content display PCM 5.1 in sonos app. Very weird 

Your problem might have something to do with this:
https://www.reddit.com/r/sonos/comments/rn47wf/latest_samsung_tv_firmware_disables_atmos/

Try unplugging your TV and Arc from power for a couple of minutes and make sure your TV software is up-to-date. Also, log in to your Netflix account on a web browser and go to your Profile and set Playback Settings to HIGH.

Many thanks guys for all your inputs.

I have tried it all unsuccessfully.  I will wait for the next  samsung tv firmware update and see what happen.

I can get app display atmos while watching atmos content on Amazon prime. But still having issue with Netflix. I can assume the TV build in app has an issue? If so, can I reinstall Netflix and solve the issue?

It wouldn’t hurt to try.

Are you sure you still have a premium Netflix subscription?

Yes, my Netflix subscription is premium .

Can't understand...

@GuitarSuperstar , I found the answer in one of your responses. Many thanks. I set the audio track to original and the magic worked.