My my, " I can't get it to start once the power supply is plugged into the motherboard"
This is one Mobo I'd love to have if it ran on nothing.
Whatever the problem is , the question just doesn't make any sense.
But still, open the Motherboard User Manual, got to the section that shows Front Panel Connectors and Asus EZ Connect.
Disconnect all those fancy reset button, speaker , power button, hdd led, pwr led wires from the mobo and then follow the instructions in the manual and connect them correctly.