Question PC not posting - motherboard lights turn on and off immediately when powered on, but the RAM stays lit


Jun 23, 2019
I made a thread about this yesterday, but I figured I should make another going into more detail

Today I built a PC for my brother. When I power it on, the lights on the motherboard turn on for a second and immediately turn off, as if there was a shortage. When these lights turn on, all four debugging LED's (CPU, DRAM, VGA, and Boot) briefly turn on and off as well. The power supply fan and GPU fan start spinning, but stop as soon as the motherboard lights go out. None of the case fans, or the CPU cooler fan start spinning at all. A few seconds later the RGB on the RAM will light up, and stay on until the PC is powered off. Something worth taking note of is that when I unplug the 8 pin CPU header on the motherboard, nothing changes, which leads me to think that the CPU is either not receiving power, or not being detected. I'm unsure if this is the cause of the issue, or indication of a bigger issue. I used the paper clip test on the power supply, and it seems to be working well.

This is stressing me out badly. I'm unsure of whether or not this is being caused by a motherboard shortage, because I'm assuming the RAM wouldn't light up if that was the case. Even if it was a shortage, I would think that the case and CPU fans should start spinning before it shorts, but they're completely lifeless. I feel like this is related to the CPU, but I'm not sure what the root of the issue is. I don't know if it's not receiving power, if it's not being detected, or why either of those things would be happening. Is it possible that my CPU cooler isn't being detected?? The worst part is that I don't know if this is an error on my part, or an issue with the hardware, and there's no real way of knowing. I'm still relatively new to PC building, and this is the first build that I've done without any direct assistance, so any help would be appreciated. I would prefer to narrow down the possibilities as much as possible instead of blindly testing things

Here are the specs if that helps:

Ryzen 3700x w/ stock cooler

MSI MAG B550 Tomahawk

G Skill Trident Z Neo DDR4 3600 16 GB

Western Digital Caviar Blue 1 TB HDD

Kingston A2000 250 GB M.2 SSD

Cooler Master Master Box NR600

SeaSonic FOCUS Gold 650w 80+ Gold PSU

MSI Gaming GTX 960 4 GB
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