Recently, my Macbook Air (Mac OS Sierra) ran out of batteries. When I tried to turn it on, the screen was all black so I shut it off. When I turn it back on, the headphones don't work. I've tried to open Audio MIDI Setup, but it shows this:
As you can see, the boxes are unchecked when the volume is up, but they are checked when the volume is muted. Either way, I cannot hear anything through the headphones.
P.S.-- I've tried this before, but I don't remember what I did.