This can be an easy fix, sometimes a section of your Christmas lights may burn out. If your lights aren't lit, try our two simple problem shooting steps. The most common cause for lights not lighting is because the bulb isn't fully inserted into the socket. A light set will stay lit with a bulb burnt out, as long as the bulb is still fully in the socket. You can always take the bulb out of the socket to stay lit, it just has to be fully in the socket or fully out of the socket. If it is not fully in or out, it will not light. Second, remove the bulb and adjust the wire if necessary to see if the bulb wires are making proper contact. If neither of our troubleshooting tips solves the problem, then you may want to try one of our light keepers or another one of our light testing items.