I've tried restarting it, checking the system preferences, entering safe mode, entering diagnostics mode, checking the permissions thing, unplugging and re plugging in head phones, doing the command option r p thing. I can't figure out what is wrong. I had used it the night before with no problems to watch Netflix but this afternoon it wasn't working.
MacBook Air (13-inch Mid 2013), OS X Yosemite (10.10.2)