Having problems turning computer on

I would suggest - Worst case

1) Your power supply cannot supply the proper threshold voltages to properly run the board.
2) Your power supply is in some way damaged.
3) The power regulation on the mainboard is damaged.

Or, as I've seen quite often -

You have mixed up the pin out connection for the start/power button on the mainboard pin header with the reset header.
(or some other header connection).

All guesses but good ones.. Good Luck!

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.