Was there direct sun in your cams field of view? Was the sun hitting the lens at all?The infrared sensorlooks for sudden changes in the heat reading of the field of view.The light will only flash if you move also. If you just stand there it will reset and stay unlit till you move. Mine works great on test. The instructions say to NOT let it be pointed toward the sun. You have to pick a tree that faces the cam preferrably in North or South direction.