Check that the outlet has power
Test the plug and power cord for damage
Make sure the bulbs are seated properly
Replace any burned-out bulbs
Check for loose, broken, or missing bulbs
Inspect the fuse in the plug and replace if needed
Verify the light string is switched on
Test the lights on a different outlet
Look for damaged wires or frayed insulation
Check for tripped breakers or blown fuses in the home
Confirm the lights are compatible with the power source
Separate and untangle the light string
Test sections of the lights one at a time
Replace the entire string if damage is extensive