I recently updated to a Roku Express 4k+ and changed from my Denon AVR to a Sonos Arc sound bar with sub and surrounds. TV is an older Sony XBR49x830c that is 4K compatible. Now the only channel that will play in Dolby 5.1 is HBO Max. Sling, Tablo, Netflix, Hulu, and Amazon Prime will only play Stereo PCM on the Sonos system. I thought nothing was working but on HBO Max I get shows that play in Dolby 5.1 and Dolby 2.0. Every other channel is just stereo PCM no matter what the show is.
Everything I've been able to find says the Roku apps should be providing Dolby outputs. I thought it might be the TV but with things working on the HBO Max channel, I know that's not the case. Prior to the Arc I was using a Denon AVR capable of converting the sound to surround so this may have been going on for a while and switching to the Arc brought it to light.
Any thoughts other than another streaming device?