PC turns off, but everything is still running?

[z33gabe]

Hello, this is a new system I built only a day ago. I keep getting this thing where my PC turns off (monitor doesnt recognize anything plugged in) but the LEDs, fans, and aio is still running. I can only get out of this black screen if I hold down the power button, or else nothing happens. I did notice there was a blinking light on my motherboard everytime this occurs. This will happen randomly, the latest was when I ALT Tabbed out of LoL.

Specs:

Ryzen 7 1700x
X370-F Mobo
Corsair Vengeance 16gb ddr4 3000
Radeon RX 550 4gb
EVGA 240 aio
kingston ssd 240
1tb WD black
750 psu

 

[Paul NZ]

I would read the manual and see what that led is and what it means if it's flashing