I have the same issue -- Premiere+ with Roku OS 9.0, no longer get surround-sound. I noticed it on my DTS videos in the Plex app. Plex says that Roku is reporting that it is not compatible, and if I force Plex to send the original DTS stream there is no sound. My Yamaha AVR supports DTS so the Roku appears to be blocking it, no pass-through.
I also checked all the following settings:
- Audio = Auto, D+ DTS
- HDMI = 1080p HDCP 1.4
I no longer see a night-mode for Audio?
I believe it's called sound leveling.
From browsing this forum I read about how the Night Mode is now controlled through the playback menu (start a video, then press * key). Night Mode was enabled in that menu, and when I toggled it off, then restarted the video -- DTS worked!