If the other brake light is working and the lights on the left side (other than the brake light)are working, then we know it isn't a switch or a ground issue.
I attached a pic below showing a portion of the wiring schematic. I circled two things in the pic. First, I want you to check if there is power to the green wire at the light when the brake is applied.
If there isn't, then the next concern is the splice I circled. Chances are the connection has failed. If you look at pic 2, it explains where the joint connector is located. I will need you to check there next.
Here is a link you may find helpful:
Do this and let me know what you find.
Images (Click to enlarge)
Saturday, November 28th, 2020 AT 9:59 PM