Alright, fuses are okay what's next? Take the extra bulb that came with the set and begin at the first bulb that is out and exchange them. If the set does not light do the same thing to the next bulb. You should not need to continue using the extra bulb just use the one from the cocket before it. Assuming it did not fix the problem means it is most likely okay. Here is the problem with what I found. On my set I found two bulbs in which one of the tiny leads from the led was missing. Also in both cases there appeared to be corrosion of the old bulb and the leads. These were used outside for two Christmas seasons. The bottom of the sockets are open to water entering if the bulb is not upright. Keeping them upright is really impossible. So, I believe GE has a bad design here which allows water into the area of the socket which makes connection to the bulb. Water and electricty do not mix. Corrison starts and it's just a matter of time until the bulb and socket are shot. To prove it I removed both sockets, soldered the wires together and all was good. All bulbs now burn. I do not recomend doing this because unless you are a electronics tech. you may burn your house down and I do not want to be the one who told you to repair the darn wiring. If you have your receipt from when you purchased them I'd go back and plead my case to the store. Otherwise throw them out but!!, buy a different design next time GE or not GE.