3rd brake light is'nt working on my 99 chevy silverado?

I checked the bulb and connection and their fine. So my question is what is the wiring route? is there a seperate fuse for that light? cause my other brake lights are working fine, and the cargo lights work fine as well. any info. appreciated, thank you.

get someone with either a continuity tester or a multi-tester to chck for voltage in the third brake lite wire. There is no separate fuse for this lite.
just giving it a visual inspection willl not provide an answer.
But before even doing that I suggest you put in a different bulb because sometimes a bulb may look good but still be bad.