Motorcycle Questions? Ask a Mechanic.
These bikes should have a red power wire going to the brake light switch and then a green wire going to the brake light itself.
Check the red wire for battery voltage and see if the green wire has battery voltage when you apply the brake. Might be a fuse, wire or bad brake switch or no ground to the brake light.
Check the wires on the light for good ground and also note that it may have a led light array which might be burnt out.
Let me know what you find. Hope you have a multimeter.