Occasionally, one or more of the LED modules on the older 911EP stick products will go out. Most people believe the diode has burned out. This rarely happens. Most likely one of the two front facing screws holding the lens on has loosened a bit. To fix this simply take a screw driver (or proper bit) and while the light is powered up, simply slowly tighten the screw. It should come back on. You may need to loosen one side or the other slightly first to evenly tighten them. Good luck!