Can’t get my volume button to work at all Recently my MacBook Air stopped allowing me to adjust the volume. Whether I press F12 or F11 it shows a forbidden symbol on it, as in the picture below.



After some research I discovered there is a mute button in System Preferences, and you are supposed to make sure that it isn’t muted. However I don’t have the option to unmute it.



Anyone know what to do in this case? I’ve restarted the computer several times but that didn’t fix anything.
I've had a similar problem with other macs. Resetting my PRAM  by pressing command + option + p+ r during reboot fixed the problem for me