HELP!!!

Did Ты try rebooting?

Seriously, my sound on my computer wasn't working, I restarted it, and it worked again.

Try rebooting it.
This happens not just on my computer, but on some of my other devices too, and restarting always works for me.

Restart.

I don't know but once I had this problem and I heard faint volume from somewhere. Then I realized my headphones were plugged in and that's where i could hear from. Ты probably wouldn't make the mistake I did.