First verify the headphone cord is plugged all the way in and volume is all the way up, not down. If that's all ok, then check the headphone cord: It may have a cut or serious abrasion somewhere along its length. Probably fixable. If the cord and headphones look perfectly sound and intact though, then next step you can probably test it for continuity with a multimeter. If the cord tests good with no breaks, you can perhaps test the earphone socket next, with the multimeter... or maybe at that point just send it for repair.... best of luck with the problem, hope it's something simple for you!