I am using debian 9 with xmonad, and one time after rebooting -- no sound.
When I run
speaker-test && pavucontrol, I see that the sound is output to the built-in speakers, but I can't hear it.
What puzzles me even more is this behaviour: when I plug in my headphones, PuleAudio recognizes it and streams to them (no sound in those either), and after some time, when I unplug them the sound comes back for a few seconds (from the speakers), and fades into nothingness.
edit having tried MATE and getting the same result, I'm pretty sure it has nothing to do with my xmonad config