I found this thread that points to similar problem with the ASROCK Extreme4, the work around got my system booting up again. It fixes the symptom but not the problem. It may not be your issue though.
View: https://www.reddit.com/r/buildapc/comments/2jrt1b/psarequest_possible_reoccurring_problem_with_the/
This is the sequence that worked.
Unplug PC
remove CMOS battery
Find the CMOS jumper pins. They are a cluster of three pins on the bottom edge of the board. Third cluster in from the back edge of the board. You should find a jumper on pins 1 and 2, with 3 open.
Remove the jumper and place it on pins 2 and 3. Wait 5 seconds, then remove and put it back on pins 1 and 2.
Reconnect power and try the power button on the board. Mine started right up.
Replace CMOS battery [test it first]