Cargo lamp / 3rd brake light problem
 

Ok I've tried everything new bulbs, new fuses, tried fixing harness connectors nothing, wiring from what I can see is ok and no matter what the left light won't come on.
1999 Ford ranger xlt. V6 3.0.
https://cimg5.ibsrv.net/gimg/www.for...a889741443.jpg
This is with a new bulbs and fuses. Left light refuses to work.

Welcome to the site..
Was common for the bulb sockets to melt and expand from heat and/or the prongs inside the bulb socket to then make a poor connection. Check for voltage and a ground at the bulb socket first with a meter. Sometimes just a cleaning of the prongs and bending them a bit more closed for more tension on the bulb wires will get them working.. If one side is working and the other not,, it should be a socket issue..