Does it stop working all together or is it very faint. Mine, not for a month now, use to get very faint on me and you could barely tell it was working. Reboot would fix this. But I got tired of this and noticed after time it would come back on it's own.
Now that I think of it.. I haven't had this issue since I factory reset. Don't quote me on that. But if you wanna give it a try...