What should you check next if the fuses and bulbs are good but the brake lights will not work on a 1999 VW Beetle?

Your brake pedal, when pushed down activates a switch, usually located up under the dash fixed to a stationary point, where the brake pedal arm is hinged, making contact with the brake pedal arm at some point. When the brake pedal is pushed down, the switch activates and allows current to flow to the brake lights. Most likely, your switch has vibrated loose from its mounting, and or it is stuck. Locate the switch and check its function. It may need to be adjusted..a simple task which may clear up your problem. Hope this helps.