My MacBook Pro won't unmute, the mute symbol is greyed out and I'm unable to change it through system preferences. I've also stuck the headphones into the jack multiple times and it hasn't worked. Please help!
MacBook Pro with Retina display
Welcome to Apple Support Communities
As you already checked in System Preferences, reset the PRAM > http://support.apple.com/kb/HT1379 This will reset the speakers settings.
After resetting the PRAM, open System Preferences > Sound > Output, and you should see Internal Speakers
Reset SMC. http://support.apple.com/kb/HT3964
Choose the method for:
"Resetting SMC on portables with a battery you should not remove on your own".
Best.
Mute is greyed out!
