The specs for that PSU claim to have a 12V 4/8 pin connector. Did it come with any extra cables or adapters that you might have put away somewhere when you purchased it? Beyond that there are only a couple of things that I can think of that would cause this kind of issue. One being that the mobo is bad, which can happen, and the other being that your PSU can't support the current build (it may have gone bad or you are exceeding its capacity).