Dusk to Dawn lights have a number of common problems, the most common being that they don't turn on or turn off. Other problems include turning on and off through the night, timer issues and parts failure. Solutions range from tapping the light to replacing parts.
The main reason Dusk to Dawn lights don't turn on or stay on is that the sensor is frozen in the on or off position. The lights may also be turning off frequently at night because the sensors are detecting the light from other sources or from the lights themselves. If the lights are controlled by a timer, the timer may become out of sync due to Daylight Savings or other reasons.
More complex lights, such as lights with motion sensors, are more susceptible to damage from weather and power surges. Lights often require specific replacement parts, and an incompatible bulb, photocell or insert may cause problems.