If your solar fairy lights aren't working, it could be because: 1. The batteries need to be replaced. 2. The solar panel isn't receiving enough sunlight to charge the batteries. 3. There is a problem with the wiring. 4. The light bulb may be burned out. 5. There could be moisture in the light fixture, which can short circuit the electronics. To troubleshoot the issue, first check the batteries and replace them if necessary. Then, make sure the solar panel is in a sunny location and not being obstructed by any objects. If the problem persists, check the wiring for any loose connections or damaged insulation. Finally, replace the light bulb if it appears to be burned out. If you can't identify the issue, contact the manufacturer for further assistance.