Computer turns on then off very quick

[Titan343]

Hi, I built a PC for a friend roughly 4 days ago and now there is a problem. It worked fine for a couple days but now when the power button is pressed the PC turns on for half a second and the fans move a little then they all turn off. It won't boot again unless you turn on and off the power supply. It is an ASUS motherboard and the little orange light on the bottom right is light all the time with orange, which I believe indicates that power is getting the board, correct? I searched through previous problem threads and tried a couple solutions that I could on a time crunch but none worked. I've tested the RAM, I don't think it's the PSU since power is getting to the board, I checked all the connections to make sure that they are firmly in place, I don't think the motherboard is screwed on so tight that it is shorting on the case, and I tried disconnection hard drives to see if that would do anything. This is the 3rd computer that I've built and I have not encountered a problem like this before. Any help is greatly appreciated!

Spec List:
Asus - STRIX B350-F GAMING ATX AM4 Motherboard
AMD - Ryzen 5 1600 3.2GHz 6-Core Processor
CRYORIG - H7 49.0 CFM CPU Cooler
G.Skill - Ripjaws V Series 16GB (2 x 8GB) DDR4-3200 Memory
Corsair - RMx 650W 80+ Gold Certified Fully-Modular ATX Power Supply
XFX - Radeon RX 580 8GB GTS XXX Edition Video Card
Phanteks - ECLIPSE P400 TEMPERED GLASS ATX Mid Tower Case
TP-Link - TL-WDN4800 PCI-Express x1 802.11a/b/g/n Wi-Fi Adapter

 

[hang-the-9]

if you are sure the system is together properly, CPU seated, motherboard in the case properly with stand-offs, etc.. then hardware is the only thing left to test. Start with contact Corsair for the power supply.