I installed a Leviton PR180 a few months back and it has been working great, that is until yesterday. We had a few momentary power outages, and after the second one the switch stopped working. There is power going into the unit, but no green light on the sensor. I checked all the cb's/fuses and gfi's but all were good. Is there an internal fuse on this unit?

There is no serviceable parts inside. There must have been a switching spike of brief high voltage that destroyed an electronic part inside. All you can do is replace the sensor.

If these types of power outages are common, even if their not, whole house surge protection at the main panel may be in order.