There might be a break in the wiring.
may be the connector that the bulb plugs into
Depends on the vehicle. Resubmit your question with vehicle make, model and year.
REPLACE THE BULB
The left brake light works the right brake light doesn't and the bulbs is good
probably your blinker switch (multi-accessory switch). The high mount brake light is wired directly from the switch on the pedal but the rear two lights are wired through the pedal switch and then through the the blinker switch on the steering column. Almost all of those blinker switches go bad.
Hmmm, kind of unusual because the same bulb filament serves BOTH the blinker and the brake function. It could be a short in the wire from the brake switch leading back to that particular bulb and if the left brake light work okay it would have to be somewhere AFTER the wires leading to the rear lights branch off from one another. Are you CERTAIN that the right rear signal blinker DOES work?
Nonfunctional Brake LightsOne possible cause of this issue is that the brake light switch is not adjusted properly, or the switch could be defective.
Black=Ground Purple=blinker Blue=light+brake
change the light bulb,
try changing the build i think it has a double fillement build that works with the brake light and blincker
no, just one solid one, also used as the blinker.
Check the brake light bulbs, Check the brake light fuse, Check the brake light switch, In that order.