new X470 Master SLI no screen

Hey everyone,

I've been hired by my neighbor to assist in building a new gaming rig, based on the Ryzen 7 2700X.

His rig so far:
AMD Ryzen 7 2700X
ASRock X470 Master SLI/ac
16GB kit of G.Skill Trident RGB (tomorrow I will have part numbers)
1TB Crucial NVMe SSD
EVGA GeForce GTX 1660 Ti

I pulled the memory HCL before I head over tomorrow morning again to help him troubleshoot.

I'm trying to rule out everything else before telling him to RMA the motherboard. Unfortunately, I do not have any other AM4 processors to test the CPU.

Basically, we plug everything in, turn it on, and no fans, no display, and only a red LED with a breathe effect displaying underneath the chipset heatsink. I do not get any beep codes, and I only wish I had a POST card or something like Dr. Debug.

At home, I grabbed an old GPU from an old rig for testing. I'm sure that it will have no problem driving a Radeon HD 5670.

Any assistance with this would be very appreciated. Is there something I missed? Newbie mistake? This is my first time assembling a rig from scratch since at least 2013.

Thanks in advance, and Don't Forget To Be Awesome...

I think I have a suspected cause of the failure to POST.

Either one of two things is stopping it from POSTing.

First, the M.2 NVMe SSD we inserted into M2_2 instead of M2_1. This might be confusing the board, but it should still post, in theory.

Second, I had the RGB LED cables going from the Wraith stock cooler going to both the PWM and the USB headers, and the manual states only one can be hooked up at once.

G*d I feel like an idiot if one of these are the causes. I'll feel even worse if those don't fix it.

If I still have trouble, I will have my neighbor contact Newegg for possible RMA.

Thanks in advance for any help. :)