What is wrong next to my motion detector street lamp? My motion detector suddenly quit coming on at night. I saw...

My motion detector suddenly quit coming on at night. I saw that here is power, I hit the test button and it lit. Does anyone know what it might be?
Answers:    Try cleaning the sensor.
enjoy you tried cleaning off the sensor?some times the sensor get hold of dirty and wont pick up motion.all so cause sure the position of the sensor hasn't changed .if it dropped down, or tilted.that could interfere with the sensors, faculty to do it,s job.i,m assuming it,s the type that have one or two lights above a sensor that can be set in masses different positions.