apple tv 4k + sonos arc + samsung serif

My Samsung TV is a similar age, but menu setting names might be slightly different. I have the same setup and can play Atmos. My settings:

TV:

Settings / Sound / Sound Output: Receiver (HDMI-eARC)

Settings / Sound / Expert Settings :

• HDMI-eARC Mode: Auto
• Digital Output Audio Format: Pass-through
• Dolby Atmos Compatibility: On

Settings / General / External Device Manager / Anytime+ (HDMI-CEC): On

Settings / General / External Device Manager / Input Signal Plus: ON FOR ALL HDMI INPUTS!

Apple TV

Settings / Video and Audio / Audio Format: Dolby Atmos On.

Also ensure the content you are playing is actually in Dolby Atmos, and that the streaming subscription you have is premium enough to include Dolby Atmos.

One more thing - check your HDMI 2 port is HDMI 2.0 and not HDMI 1.4 (if not, swap to an HDMI port that is), AND that you are using a High Speed HDMI cable - both are essential for Dolby Atmos. 

The sonos Arc is connected to ARC port and the apple TV to HDMI 1 the content that I watch on netflix support dolby atmos but still The apple TV is not playing dolby atmos just playing dolby surround sound 5.1 

Did you see my earlier reply, not just my last one? Have you compared settings?

I did see you reply I checked everything and this is my TV settings

I’d try changing PCM to Bitstream. 

I can only choose these two options. I Can’t choose dolby digital+

And just to be clear - all the other settings I posted match on your TV (eg Input Signal Plus, etc)? 

Yes all the settings are the same 

One final question - are you using the Sonos HDMI cable for the ARC, and are you using a high-speed HDMI 2.0 cable for the Apple TV?