Check the bulbs and fuses and if both are good and lights still won't work try disconnecting the fog light connector from the harness and make sure you don't have water in the connectors. Do the same thing with bulb socket. If there is water in the connectors, either leave them disconnected for a bit and let them air dry or use compressed air. Use some dielectric grease when reconnecting. If they still won't turn on after all this use a volt meter and see if you're getting any power.
Almost every time I wash my truck my drivers side fog light will stop working from water getting in the connectors. But it always turns back on after I drive around for 15-20 min and it dries.