I'm putting together an i5 4690 with a MSI Z97 U3 Plus motherboard and I have an Antec 750 watt power supply. When I push the power button on my case nothing happens. A couple of times it turn on for half a second then die. I have a good power cord. I have the 6 pin plug into the motherboard because it won't take all 8 pins and double check my power switch which the lettering is supposed to face the outside of the board. Any suggestions?