I have a 2002 Dodge Durango the third light work but the brake lights do not work what can it be
If the "third" brake light is working the switch is okay. The bulbs have been changed, and I assume with the correct bulbs. Has there been any work done recently? Has a trailer hitch been installed? Often times the trailer people sever the wire going to the brake lights with a "scotch lock" which cuts the wire in two, although not immediately. Also you need to check the ground to the sockets. If the lights are in the rear hatch, the wires between the hatch and the body of the vehicle may have been severed due to the opening and closing of the hatch. Look for the rubber tube the wires go through near the hinges and see if one of the wires inside are broken. If so, repair the broken wire an that should fix the problem. Good luck, and I look forward to hearing the solution to your problem.
Since the high mount light works it's not the switch.
Check in the wiring harness in the left rear quarter panel along the frame. More than likely a splice/wire is rotted or broken.
There should be a ground point for the two stop/tail lamps either on the left frame or the bumper. If that's OK trace the wiring and repair as necessary.
If it is just the brake lights that are not working, the the following could be faulty -
Brake switch on the brake pedal - check that it is being actuated by the pedal properly. You cold also bypass the the switch by connecting the two terminals together and see if the lights then work.
Fuse could be blow - find the fuse and check its condition.
The bulbs could have all blown. It is possible that you never noticed when one was individually blown.