There are a lot of reasons why a light might appear DOA, among them:

- no battery contact / circuit (battery might need a magnet or something on top)

- a wire came off on the driver

- battery too short in this type of light (therefore no contact)

- polarity wrong (I guess you mentioned this one already)

- try another battery

  • try running the light without the tail cap (use a wire to bridge, this should work on lights with a manual switch and no electronics in the tail)

Even if you don’t mod lights on a regular basis, BLF is a great community and can help with issues that may come up. I would try a few things and then open up the light to see what it is.
A long time ago I also won a light on a different forum and the C8 came in DOA. The (+) wire came off on the driver, soldered it back on and that was it.