What did Sonos support suggest to you when you submitted a diagnostic, and called them?

I was told, there did not appear to be anything was wrong and that they were sorry the quality did not meet my expectations.

What audio format does the Sonos app display when watching 5.1 content from Netflix?

So I played a movie on Netflix (not sure how to see if it is 5.1 content).   But Sonos app says Dolby Digital Plus 2.0.

What model TV do you have? What audio format does the Sonos app display when playing the film Don’t Look Up on Netflix? Have you tried adjusting the Sub Audio level in the Sonos app? Have you enabled the Loudness setting and disabled Night Sound (moon icon) in the Sonos app?

TV is a new Sony Bravia XR65X95X.  Sonos app says Dolby Digital Plus 2.0..   I will try the other settings you suggest. 

Set the TV to the settings below and test the audio again. You want to see “Dolby Digital Plus 5.1” in the Sonos app.

eARC: Auto

Digital Audio Out: Auto 1

Dolby Digital Plus Output: Dolby Digital Plus

Pass Through Mode: Auto

The 2.0 in Dolby Digital 2.0 means there is only a right and left channel of data. The .1 in Dolby Digital 5.1 is an LFE (Low frequency effects) channel. When using a 2.0 signal , there isn’t anything being sent to the subwoofer for it to play. 
 

Follow @GuitarSuperstar ‘s suggestions, make sure you’re testing with a Dolby Digital 5.1 source. Sometimes, you need to go to a movie channel to get a good test signal. Most content on YouTube is *not* 5.1 at all. 

I ensured those settings are set.  When watching Netflix or Amazon prime Sonos app says Stereo PCM. Watching cable TV sonos says Dolby Digital 5.1.  

Playing music with sonos app and Pandor, sound is flat, no bass.

Are you using any external media devices or are you just using the TV’s native apps?

I am using a firestick for Netflix and Amazon prime.   Music is through the sonos app on my phone linked to Pandora.

On the Fire TV Stick, go to Settings > Display and Sounds > Audio > Surround Sound and select Best Available.

Also, try testing the TV’s native Netflix and Prime Video apps.

OK I will try that.   Thank you. 

After selecting Audio there is no option for surround sound.  There is an option for Dolby Digital Output >Dolby Digital Output,  and that is OFF.

That should be switched to On.

I turned that on and selected the option Dolby Digital Plus over HDMI and that seemed to help.  Playing from the Firestick now shows Dolby 5.1 on Sonos App.