I have the exact same issue, I can no longer mute/unmute my tabs by using the icon.

If I open a second Opera browser then the mute/unmute works there. But I don't want to move my tabs to the new browser window because I'm worried tabs might get lost or that opera won't recognize the new browser window as the main one.

Only way I can get my tab mute icon to work is to pin all my tabs. For me it only works on pinned tabs. I really hope there will be a fix for this soon.

I have the exact same issue, I can no longer mute/unmute my tabs by using the icon.

If I open a second Opera browser then the mute/unmute works there. But I don't want to move my tabs to the new browser window because I'm worried tabs might get lost or that opera won't recognize the new browser window as the main one.