Help & troubleshooting for channels on your Roku device, including adding/removing channels, logging in to, authenticating, or activating a channel, channel-specific playback issues, assistance contacting channel publishers to report issues, and adjusting channel-specific settings.
A few people in here figured out that when you pause youtube and press the * the sound comes back for that video. You need to keep doing that unless you do what RED808 said to do... while on yt go to volume and turn it off, then the sound is on.
It's still a little wonky inbetween sometimes and I hope they fix it but for now this works the best.
I posted the solution many many messages ago: Press *, scroll to volume mode and switch it to off or normal while a video is playing and the sound should return instantly. Make sure it's not up loud so speakers don't blow. Unfollowing this now because I'm getting annoyed that people are not reading and doing as I suggested, besides a few.