Driver side brake light not working

Since the right side is working, there is not much that can go wrong on the left side. Terminal six should have a pair of white/tan wires. One goes to the right side, so we know the twelve volts is making it that far. Look at the pins of that connector. If they are soldered to a circuit board, look for bad solder connections. If that is a flexible plastic overlay, those often develop breaks in the copper traces. Remove the brake light bulb, then check for twelve volts that shows up on one terminal in the socket when a helper pushes the brake pedal. If that twelve volts does not show up, see if you can find the break in the circuit. If it is inside that flexible plastic, you may be able to solve this by running a jumper wire between the bulb's socket and the assembly's connector.

Please let us know what happens, we are interested to see what it is.

Cheers, Ken