I have a steaming stick + connected to a samsung tv. I'm testing roku with the PBS app and Sling. Of course there is no mute button. For both, when I hold the voice command button and say "mute", messages appear on the screen ending with "Toggled Mute" but the TV is NOT muted. Interesting that while the command is running the sound is muted but sound comes back when the command ends. Voice command for closed captioning works great.
I wasted a lot of time with support. It's off shore support so I did a chat to avoid accent and language issues. After an hour or so, the rep seemed to understand the issue but was clueless and gave a BS answer that he couldn't explain.
Any ideas before I write off roku? With no way to get meaningful support and no way to mute, that's what I'm ready to do.