After you have done the first two replys, and that is not the fix get a test light and test the brake switch and hazard switch at their outputs and that there is power. The bulbs are one of two types either (A) dual filament (Brake-Turn and Hazard-Driving) if you notice all these functions share that socket or sockets,or (B)single filament (one pair of functions or the other) meaning two sockets one for brakes/turn and one for driving/hazard.Normally if it doesn't light at all it could be bad bulb or bad or no ground or no signal.If both tailights have same problem then I would go to the source of each circuit after checking bulbs and grounds(unlikely being they don't share bulbs and grounds on pass/driver sides but I have seen stranger things)Check to make sure your flasher actually is good(New doesn't mean good)Luckily your wiring harness is color coded so it will be easy to track down your circuits the under the dash part is going to be tough.Oh yeh you will need a capture style test light(about $20) it has a hook on the end to hold the wire while the test pin punctures outer insulation.
