I see two potential problems here:
Either your psu got overloaded ( or overstressed when you turned your pc on after rebuilding) and fried your motherboard or you fried your motherboard with static electricity.
Other possible problems:
-any extra standoffs touching motherboard circuitry
-All ram sticks properly seated in each slot
-4 or 8 pin cpu power cable not connected
Is your power supply toggle switch in the "on" position?