I have this problem from time to time and it is getting pretty frustrating. Each time I must 1) unplug and then plug back in the power, 2) reset the Roku. Sometimes I must reset the Roku 2-3 times and/or wait about 15 minutes for the Roku to apparently clear out the **bleep**. Nothing like sitting down to watch TV in the evening and then spend 20-30 minutes trying to get it to work.
My ROKU Ultra purchased June 21, 2021 is requiring a reboot every two hours in order to get the audio to work on any streaming channel. System sounds still sound normally but no show will have sound until the ROKU is reset or rebooted. From reading the comments here and in other places about this topic it seems as if ROKU knows about this but has no idea on how to permanently fix it. I watch two episodes of a show on the CW and on the third: NO SOUND. Reboot the ROKU and it works normally again but multiple resets every single day is NOT ACCEPTABLE!
saw Amherst in your name and wondered if this was Amherst Virginia. I'm mbgva and live in Lynchburg. The reason I ask is I use XFinity for Internet and wondered if it might be part of the problem. If you live in Amherst Va and also use XFinity, we are probably being served from the same hub. I'd say that the possibility of XFinity being part of of the problem increases in that circumstance.
I live in Wisconsin and do not use Xfinity and am having the exact same problem as Amherst, but when i watch, weirdly, the Big Bang theory. Therefore, I agree with Amhearst, this is a larger, systemic problem that Roku is clearly aware of.
Sorry, Amherst Ohio but I use the same name in a social game so I'm learning about all the other Amherst in the world which is interesting. My internet provider is Spectrum and I don't think their service is causing my issues as I don't have issues watching the streaming channels either on my Windows 10 PC using Chrome or the apps on my LG Web Is TV. The ROKU issue started a few months ago according to my Aunt who uses it more than I do but she just gave up on watching tv when it happened and turned everything off for a few hours which temporarily resolved it. Without a blizzard or rainstorm to trap me in the house I don't tend to spend multiple hours watching tv at a time. When I do however I binge watch as I'm to lazy to change the channel/network to watch something else. Hallmark all day is fine when we're getting a foot of snow dumped on us. (I sew, do puzzles, play my social game on my Kindle fire and do diamond painting while watching TV so unless it rudely goes silent or shuts off I'm fine.)