LED Christmas lights are a little more difficult to repair than older iridescent lights as you often cannot swap out the bulbs. More often than not, a fault with this type of bulb is caused by a faulty wire, more than a broken bulb. It may be that a wire has been broken or frayed when in storage, or there is an issue with the fuse or plug. These issues can be fixed if you have some understanding of electricals, but it may not be as simple a task for those of us less in the know.