If by 'none of them are working' you mean none of them light at night I would first of all suspect a fuse, battery feed, ground, voltage stabilizer or some other common denominator (actually I cant think of another!). You should be able to at least feel whether the bulb(s) are in place. Should be fairly simple to find the fault.
Mine were all missing as the yahoo that finished the car for me misplaced them ALL!
Paul