What model TV do you have? Are you sure Maverick is available in 5.1?

Since it works for current TV shows, that means there is nothing particularly wrong with the Sonos, so you need to look up chain. What audio format is the movie Maverick being played with/in? Do you have your Apple TV’s audio settings to convert to another format, or pass through? Can your TV set pass through the audio properly as it is received from the Apple TV?

My initial guess is that Apple TV is playing a DTS soundtrack, which is being passed to the TV, which isn’t able to process it, so the TV is grabbing the stereo signal and passing that to the Sonos….but that is all conjecture.

One thing I’d definitely try is going in to the Apple TV’s audio settings, and try changing it to Dolby Digital 5.1 only (not looking at my Apple TV at this second, it’s something to that effect) and see if it then plays in 5.1 on your Sonos. 
 

There may be settings you need to adjust in your TV’s settings to pass through DTS, or it’s equally possible the TV set can’t pass it through at all. 

LG TV  65UM 7300 PUA. According to the paramount plus site, Maverick is available in Dolby Atmos.

Tom Cruise Maverick, Mel Gibson Maverick, or James Garner Maverick? 

Sorry I should have clarified Tom Cruise Maverick 

What is the Digital Sound Out setting on the TV currently set to? Is there a DTV Audio Settings option on the TV too? Is your Apple TV an Apple TV 4K model?

The Tv is set to auto the Apple TV is the 4 k model

the arc is pass thfu

Recently my setup has started to default to stereo pcm on some tv series I own on apple tv 

If I watch something else that is dolby 5.1 and switch back to the series I was watching it is back in 5.1 it is intermittent but irritating 

My atmos movies are ok just tv series that it happens on it is a recent phenomenon 

wow, that sounds unusual. this has been happening from day one about two weeks. 

Because your TV isn’t equipped with eARC, you cannot play Dolby Atmos audio from the Apple TV 4K. You need to change the audio settings on the Apple TV to this:

Change Format: ON
Audio Format: Dolby Digital 5.1

On the TV, set the Digital Sound Out setting to Pass Through (if available). If not available, keep it set to Auto.

Thank you I will let you know how it work’s

Hi again,

An eye opening experience. For some reason it became necessary for me to restore my LG TV to factory settings. Once finished everything immediatly sounded better. The apps now play thru the ARC and the audio is playing correctly. atmos, dd+ etc. all sound great. I didn’t think this was possible. The good part is I guess I won't be spending on a new TV with eARC, and also I won't be using my Apple TV as much.

Thanks for the help

Sam