My friend has a Black Macbook from a couple years ago and is having audio issues. The computer is fully updated and has been rebooted numerous times. The problem is that the Mac's volume won't work. When she presses the volume buttons on the physical keyboard there is a gray circle with a slash through it that appears on the screen. She has tested headphones and they work, but not good quality wise. The audio output and speakers are set up correctly in System Preferences (I compared them to my MBP). Also, there is no digital out or red light coming out of the port, so nothing is stuck. What should she do, is this hardware failure?