Did you change the settings on the Apple TV to output lossless audio?

Apps > Music settings:

Dolby Atmos: Automatic

Audio Quality: Lossless

Yes i did this but still no lossless

Stereo PCM can still be lossless. When streaming Apple Music from the Apple TV, the Sonos App will not display the Lossless logo like it does when streaming directly from the Sonos app.

But when i stream from the app i get all my 5.1ch working arc ultra + sub + 2 era 300.  From the apple tv it’s much worse only 2 the arc working

TV sources will play as is.  If it is stereo PCM, it will play as stereo.  Music sources (not playing on the TV) will be played in all speakers at the same volume (‘Full’ setting) or through the fronts at full volume and ambient through the rears (‘Ambient’ setting). 

It’s the difference between TV mode and music mode.

When streaming stereo content from the TV, the Arc Ultra will perform an up-mix of the stereo audio and send what is determined to be ambient audio to the surround speakers to simulate surround sound.

When streaming stereo music from the Sonos app and the Music Playback setting is set to Full in the Sonos app, the surround speakers will play in full stereo.

Only when i set the audio option on the apple tv to use temporarily sonos sound system i get all 5.1 speakers to work but it is temporarily. By default i get tv speakers to work with apple tv sonos app and stereo pcm.

nothing i do change that.

You aren’t going to get Apple TV to play music in 5.1 unless it is encoded in 5.1.  Sonos simply doesn’t convert a stereo TV source to play in all 5 speakers like it does streaming music. Stop thinking that it is possible, it’s not.  If you wish to get stereo music playing in 5.1, use the Sonos app or Airplay.