mine has done it before. First just pop the cover off the lens. Next get a small flathead. On one side of the round light housing there will be a bit of a flat spot you can get the flathead under and just gently pop it out. comes out easy. NExt is to look at your connectors. Either they had them off and missed one prong when putting it back in , or you have a loose pin connector. If so push it back in. If you haven't water proofed you should consider that while your in there. There are great how to's in here just look around.