You might have a parasite voltage drop. If you have a multimeter you can find the problem in about 10 minutes. Parasite in this case means someone else consumes the voltage or may be an open circuit. Remove the bulb depress brake pedal and check voltage at the socket. If Nothing, take the négative lead and connect it to a know good ground, Recheck voltage, if you have no reading connect one end to the ground of the socketand the other one to the positive of the batterie if you have 12 then start to go towards the center of the carpedal switch, flasher unit etc. also check the connector in the trunk.
Fast explination if you have any question you can pm.