Some TV’s can’t pass Dolby Audio through from external devices.  I have a TV with only an ARC connection and had to use an Arcana HD Fury device to split the Audio and video.  This enabled me to send the Audio directly to the Arc, rather than through the TV, and the video to the TV.

Edit:

Diagram of my setup attached.

An ARC connection can pass Atmos as DD+, but not all TV’s support it.  List your TV model and we can look up the specs. 

Jgatie-

I have a Sony model XBR-65X900F, about 6 years old. 
 

Thanks

As far as I can see, that TV was upgraded to DD+ Atmos support by a firmware update in 2020.

My Sony TV is also a little dated and no eARC. The format arriving on the Sonos depended on the streaming app on the AppleTV 4K, super wired.

if you don’t plan to buy a new tv soon https://hdfury.com/product/4k-arcana-18gbps/

will give you Atmos TruHD if you use any source that supports it