If it is a brand new motherboard that hasn't been used before, it may be defective. My first UD3P board was bad and had to be RMA'd. Test it outside the case with just CPU, HSF, Memory, PSU, monitor attached. To start up, short the 2 pins the power button would connect to. See if you get a display and can boot to BIOS. If not, I would RMA the board.