Motherboard won't start. What to do?

Question

Iron

Good afternoon, comrades. I ran into a problem, I'm assembling a computer for a friend:
Motherboard ASUS ROG STRIX B360-H GAMING
Processor Intel Core i7-8700K BOX
RAM Kingston HyperX FURY Red [HX426C16FR / 16] 16 GB
Video card Asus GeForce GTX 1080 Ti STRIX OC.
With a completely correct connection (not the first time I collect), the motherboard does not start. For half a second it gives power by turning the coolers and turns off. I tried to turn off everything, including the video card and RAM, but at the same time, I did not take the mother out of the case. Standby meals, when idle, are on the map. Today I'm going to try to run it on the stand, naked, with a different power supply. What else could be the problem and what needs to be tested before being assigned to the SC?
UPD: Thanks everyone! It turned out that the power supply did not give 12v. Got a defective one from the factory. DNS was replaced at the moment

Answer 1

Possible reasons:
1) The problem with the PSU. You can try with another power supply
2) The problem is with the processor. It is solved similarly to the first problem
3) The problem with the mat itself. payment. Try to visually inspect for swollen conders, etc.
4) Problem with UEFI. Unlikely, but quite possible, that the problem is with the firmware. It is solved by flashing in the SC.

Answer 2

Shorty. The power closes somewhere to the case, an anti-short circuit is triggered in the power supply unit and it is cut down.

Answer 3

Maybe Mat, the board is shorting somewhere with the case. BP goes on the defensive.
Try resetting the BIOS (removing the battery for 5-10 minutes and putting it back in). If that doesn't work, take it back to the store. Possibly marriage.