I put my HIDs in, but my drivers side didn't fire up. So I changed ballasts and bulbs and still doesn't. So I threw my stock light back in and it didn't work either. I put a test light on the plug and it light up. What's the problem???

 

i had the same problem. realized i plugged it in backwards.. try turning it around

 

on some kits the wires at the factory headlight clip need to be reversed.

did you try the ballast that isnt turning on; on the other side to see if the ballast and bulb are functional?
if they are, you may need to install a relay. if not...im sure you can figure that part out

when i bought my truck 2 years ago it had an HID kit and needed a relay to work. sometime the driver side light would go out and you would have to turn the light off then back on for them to both work again.