Mac Book Pro Headphone jack isnt working?

How old is your MacBook Pro, and do you have Applecare? You might still be under warranty.

Otherwise, have you tested your headphones out on another device and tried a different headset on your Mac? Is the channel completely dead, or can you apply slight pressure to the plug to get the channels to work?

Maybe answers to these questions will give clues to others here to help.

This is strange. Mine stopped working the same day. Wonder if there was an update?

I'm having the same problem... only the right audio channel works via headphones. Suddenly stopped the other day. Speakers are totally fine. Headphones as well.