PC Won't Boot (Down to last step troubleshooting)

glamourswinexxx

Prominent
Oct 29, 2017
2
0
510
Hi there Tom's Hardware... first time posting here so thank you for any feedback you can offer!

I've recently purchased all my computer parts for a new PC build.

Relevant Specs:
-ASRock Gaming K4 - AB350 Motherboard
-AMD Ryzen 5 6-Core CPU
-2x8GB G.SKILL DDR4 RAM 3200
-EVGA 1060 GPU
-Cougar 600W PSU in Cougar case

I've got everything assembled and the dreaded "nothing fires up" at all. No lights, no fans, nothing. I've been troubleshooting down to bare bones with no luck on a boot up, I'm hoping I can get some help here. Thank you!
-I've tested the PSU with the paper clip trick and the PSU fan works (I had this PSU in a previous PC so I'm 99.9% sure this wasn't the issue), and the HDD and CD drive make their 'boot up' click noises. No issue there.
-I've cycled the RAM sticks one by one in each slot, no luck in booting. RAM seems to be fine.
-I've tested with and without the GPU in. Seems to be fine.
-I've popped the CMOS battery in and out multiple times
-I've brought the mobo onto my desk (with foam/static-guard underneath) and have only the RAM, CPU, and mobo power plugged in, and still no firing up.
-Another note: when my mouse is plugged in to mobo USB and the PSU was in the "on position" the led on the mouse lit up (does this mean power is correctly flowing through mobo if it's making it to USB?)
-Second note: I've taken the case power button out of the factor and have been jump starting the +/- on the mobo. My desk light is on the same circuit and when I attempt to boot the light flickers a little like the PC normally would kick on (so it's trying to pull it's boot power for a split second it seems) but still no load up.

This leads me to believe the mobo or CPU is DOA, can anyone offer me insight onto which it is? Or how to test one versus the other? I have a few days left to get a return on the CPU, but would have to go through the manufacture warranty on the mobo if I need to replace either. So time is of the essence for me haha.
Thank you very much!!!
 
Solution:

Update for helping anyone out with a similar issue- my ATX pins from my PSU were incorrectly inserted. My PSU had two separate sets of the 4pin ATX connectors that provide additional power to the motherboard, and I had the wrong ones in. Such a slight oversight set my whole build back!!