Fixing LED Christmas lights can be a bit tricky, but there are a few things you can try to troubleshoot the issue. First, check the bulbs to see if any are burnt out or loose. If that's not the case, then check the wiring to make sure there are no broken or frayed wires. You can also try replacing the fuse if the lights aren't working. If none of these solutions work, then you may need to replace the entire string of lights.