so its 500w and seems to be able to have 2x6+2 pin cables so modern enough to suggest it would be good enough to do the work it needs to do.
and you have it plugged into the closet slot to the cpu (slot 1 that has a clip ), if your able to test it another pc maybe to make sure it is working, or if it new go back to store and ask them to test the video card because it is not working.