Whos got the Simgma 500 Super w/ a XT??

I need some help. I think I have a defective flash, but i want to make sure before i send it back to the person i bought it used from. he say it worked with his 300d when he mailed it.
i posted about this already and didn't get much answer....heres the post link
http://www.photography​-on-the.net/forum/showthre​ad.php?t=138931
so i'm not getting the lightening bolt in my viewfinder, the flash can recognize when i change ISO setting on my camera, and i get the red light shining when i push the shutter half way, but the flash never fires! the bulb is fine becuase it fires when i hit the test button.
i'm not sure if i somehow have a setting wrong or waht, could someone who uses these 2 together please help me out? what settings should i have both the camera and the flash set at to test and see if it works? any other suggestions would be great too.

Check that the flash hasn't been disabled by a custom function, either in the camera body or on the flash (not sure if the 350D does that). Try it on a different camera, or try a different flash on the body. Make sure the flash is seated properly. Not sure what else you can do.

i have tried the flash on other cameras and it hasn't worked. i also tried a different flash (canon) on my camera and it fires fine. i can't find any stores in my metro area that has this flash to test this flash with my camera.
the guy that sold it to me suggested i try it with a 300D (the camera he says it works with) but i can't even find a store that carries that model anymore, they all have the rebel xt. ARG!

contact the seller and get your money back....

I would have to agree with John. What if you find a Drebel and it works on the Drebel? I'm assuming that you bought it coz he tested it on a Drebel BUT the expectation is that it will work on the XT and other cameras.