Works half the time, very inconsistent.

Response to the dev -
It's completely random. sometimes it works and other times it doesn't, will post an update if i find out anything. Perhaps it could have an issue with another twitch extension i have, BetterTTV, FrankerFacez, Unwanted Twitch.

Update 31/5/24 -
Still randomly decides to play audio in an ad, i disabled the extensions mentioned above and issue remains, have no idea what is causing it, it's completely random. I would say it mutes 90% of the time but then randomly an ad will start playing with sound, very annoying. To fix it i usually have to fiddle about with restarting the page and disabling/enabling the extension.

You mentioned multiple tabs, not sure if that is still the issue or if you have actually fixed it, i always have multiple tabs open in Firefox, at least two at any given time, so perhaps it's still causing an issue.