I’ve had this bizarre issue where most videos online, be it on Twitter or Youtube had sound, I had sound in Musicbee and in video players, but there were some videos online that were just dead silent. It looked like audio is playing, but I couldn’t hear anything. Couldn’t figure it out for a while till it hit me I’ve done a soundcard driver update recently. The reason was I’m using 2.1 speakers and the soundcard reset itself to 5.1 mode after driver update.
When this happens, videos with mono sound won’t play any audio at all because the mono channel is expected to play on a center speaker which, with using 2.1 speakers, you do not have. Switching back to Stereo mode in soundcard settings forces mono sound from non-existing center speaker into both stereo channels and sound should “appear” again.
So, if you’re having such problem, check your soundcard settings speakers mode to see if it changed by itself to 5.1, causing this problem…
Hope this helps 🙂