Question Installed new PSU, now PC won't boot.

Aug 5, 2020
I upgraded my PC a few days ago with these new specs:

CPU - AMD Threadripper 3960X 3.8 GHz 24-Core Processor
Motherboard - Asus ROG Strix TRX40-E Gaming ATX sTRX4 Motherboard
RAM - Corsair Vengeance RGB Pro 32 GB (2 x 16 GB) DDR4-3200 CL16 Memory
Cooler - Corsair H100i RGB Platinum

other specs I already had/have in the build:

GPU - Nvidia Geforce 1080 founders edition
SSD - Samsung Evo 850 & 860
Windows 10

I took all of my old parts out, added everything that I listed above, and was able to boot up my PC. However, upon booting I received a message saying that my PSU was under the recommended wattage (which was 850, my PSU at the time was 750). I WAS still able to boot though, and run the computer normally, with a risk of course.
I did not want to use the CPU with this risk so I ordered a new PSU:

Corsair RMx (2018) 850 W 80+ Gold Certified Fully Modular ATX Power Supply

Now, after installing the new PSU my computer will not start. The motherboard will light up, so I know it's receiving power, and when I hit the power button the CPU Cooler fans, and the GPU will turn on, but immediately stop working. The RAM will stay lit up as long as the PC is on, but nothing else seems to be working.

I have checked cable connection multiple times, and rewired multiple times. ANY IDEAS???
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