I have a double switch. The top one controls the security floodlight and is working fine. The lower swith operates the coach lights on both sides of the garage door. This switch doesn't work. What should I look for. I have already checked circuit breaker box and all ground fault interupters.

Check for power out of switch. I would suspect that first as 2 bulb don't Usually? Blow at the same time. A know good bulb would be a good test.

Agreed, start by checking the switch for power coming OUT to the lights, could just be a bum switch.