I have a single lamp magnetic 40 watt ballast, I wired it to my strip light, stripped paint off it for better starting, grounded the light, and it STILL doesn't light, I get a loud kind of clack noise when I turn it on. What's going on?

It is preheat or RS? HPF or NPF?
You will have to do some troubleshooting with a multimeter...
Striping paint does not make any difference, as the shield is used to provide capacitive current, what does not depend on the material on the conductor surface (the lamp glass is an insulator too). Issues might be caused only by humid dirt on the glass (=insulator) surface, as it make resistive shield.

it's a LPF single lamp RS ballast, and I figured out the problem, it has a shorted winding! I let it sit for a few minutes and it heated up fast!

Medvid, I told Rudy to strip some paint off the area where the grounding wire and screw connects, because rapid start maganetic ballasts setup needs good grounding for proper starting. In my old house we used to have a major problem with our 2 X FB40T12 fixture (40 watt U tubes) we tried new lamps, new ballasts and all, most of the time it did not solve any problems sometimes it worked sometimes it wouldn't....but when I stripped paint off where the copper grounding wire connects...voila it worked. You know dirty tubes can prevent rapid start from starting....