I'm at my wit's end here. Still at this new build. I5 gigabyte z87n. This system will not even turn when the 2x2 12v power connector (next to the CPU) is plugged in. If just the 24pin connector is plugged in, the system will turn on (fans spin, etc) but will cycle on and off over and over (as the 2x2 power isn't plugged in, it won't continue.
I have tried two PSUs with same results, tried mono, CPU, PSU only, one ram, both ram, etc. I'm just confused. This mono doesn't appear to have a speaker either so there are no POST sounds. =(
Try just MB, CPU and PSU outside of the case. If the CPU fan runs, add ram and use the integrated graphics.