What exactly are you testing? Are you 100% sure it is a Dolby Digital 5.1 source?

I’ve tried multiple movie sources. Netflix. Amazon prime. Disney +. Multiple movies. Still nothing. The Sonos app reports Dolby digital 5.0. These are all built in apps to the TV

I’ve never been a fan of the CEC / ARC implementation on the Hisense. Have you updated the TV to the latest firmware?
 

What happens when you use a device connected to HDMI, rather than internal ‘smart’ apps?

This is the playbar so only optical is available. TV is the latest firmware. I haven’t tried other devices hooked up to HDMI yet. 

I wonder if the issue has something to do with the original audio being in Dolby Digital Plus. Netflix, Prime Video, and Disney+ all use Dolby Digital Plus for 5.1 audio. 
 

What other streaming services do you use? Do you have the Apple TV+ app? Can you test the film Mission Impossible: Ghost Protocol using the Pass Through, Auto, and Dolby Digital settings?

I have tried setting the TV to Dolby digital plus as well. Same result. 
 

I have HBO Max too. I do not have Apple TV+. Let me see if I can test that movie through any of them. 

HBO Max uses Dolby Digital Plus too. Apple TV+ is the only major streaming app I know that uses standard Dolby Digital. Would you be willing to do the free Apple TV+ trial for testing purposes? I completely understand if you don’t.

Thanks for the tip. Tried Apple TV+ and sure enough all surrounds work. That’s with the built in app on the TV. And the setting on the TV to Dolby digital plus. Will I have to use an external Apple TV for the audio to work as expected?

An external media device might work. The Apple TV 4K has a setting where all audio sources can be converted to Dolby Digital. So this might be a good option for you. If it doesn’t work, you can always return it and try a different device.

Thanks. Do you think it’s just the TV or the apps themselves? I also have a Beam setup with surrounds on my LG TV. No issues with built in apps or the Apple TV I have hooked up to it. 

I think it’s a combination of the TV, apps, and Playbar. Most streaming apps only use Dolby Digital Plus for all 5.1 audio. The TV doesn’t seem to know how to handle a Dolby Digital Plus audio mix when it’s connected to a sound bar that is limited to Dolby Digital.

Confirmed with using an Apple TV I get full surround. So it must be the way the TV is passing audio from the internal apps?