Please try an extended clear of the CMOS. Unplug the power supply from the wall or motherboard, or switch it off in the back. Then press and hold the case power on button for one minutes, then remove the CMOS battery and put a jumper on the Clear CMOS pins for 8-12 hours. Then remove the jumper, put the battery back, turn on and connect the PSU, and then see if it works.
If it does not, then the power outage could have been caused by a spike, and might have shorted out some of your hardware. To check for that you'll need to test your PSU, CPU, and memory on another board, or test different CPU, memory and PSU on your board.