It is really very strange and frustrating!!!!, but for no apparent reason there is suddenly no sound from the speakers with e.g. mp3 player, system sounds. When I try this out as well, I get no sound at all. To my knowledge I haven't changed anything or nothing is on mute.
What can I try to reset it or something else, because I have absolutely no solution myself. I have tested the sounds in Windows, and that just works fine.
The strange thing is that with this one, sound does appear with the right and left speaker test. See 2 screenshots:
