Rear Brake Light not working

Hi,
My right, rear brake light does not work.
The orignal unit filled with water, I repaced it and still the brake light did not work. I connected the replacement unit to the left side and all lights work correctly. The red LEDs function correctly for all other needs.
I believe that this is a very common problem but I've yet to find any sort of solution from internet/forum searches.
Anyone have any ideas?