Came home today to find my PC off and won't power on. The 5VSB LED light on my Z170 Stinger is flashing white next to the 24-pin MB connector when the PSU is connected to AC power. PSU is an EVGA Supernova 650 P2. Tested the PSU with a tester, powered right on. Checked 5V in the MB connector with a multimeter and got a good 5.05V. Checked 5V and 12V in one of the Molex connectors and got 5.05V and 12.33V also. MB I/O shield is not installed. Also tried disconecting the USB 3.0 header with no change.
 
Did not have any sort of power outage during the day. No power surge is obvious either. Both my PC and monitor were connected through a surge protector and all seems to be fine.
 
Any thoughts? I haven't had any issues with the PSU or MB since the PC was built in Fall 2016. Doesn't appear to be a bad PSU