1999 Buick Regal third brake light

The power for that light leaves the brake light switch and goes directly to the light so you have either a wire problem or one of the connectors isn't making good contact. It's a white wire.

How did you check for power with a test light or a multimeter?If you used a multimeter did you check for power across the power and ground terminal's of the third brake light connector?Or did you ground the black lead of the meter and just check for power to the light?