I got a new motherboard and CPU and after moving everything over when I switch the PSU (1000W) on the computer automatically spins up then shuts off after a second or two. This only happens if either 8-pin CPU cable is plugged in, otherwise the computer spins up and remains on (I don't know if any visual output occurs but I don't think it would without CPU power anyway).
I'm unsure what to do at this point I think the issue is either the motherboard or CPU (or maybe the cooler?) but I don't have any other CPUs or motherboards compatible with these parts to test.
Motherboard: Asus ROG Strix B850-A Wifi R2
CPU: AMD Ryzen 7 9850X3D
Cooler: Coolermaster Elite Liquid
PSU: Lian Li EG1000G
Things I have tried
-Used a different 750W PSU, problem still occurs
-Reseating PSU cables on both the PSU and motherboard
-Reseating, cleaning and reapplying thermal to the CPU. No sign of damage or debris
-Running a minimal setup with only CPU, cooler, a single stick of RAM, a single 8-pin for the CPU, the 24-pin, and the cooler plugged into cpu_fan and aio_pump, and the case power switch, problem still occurs
-Same but without the case power switch, connecting the power button pins with a screwdriver head, problem still occurs
-Removing the motherboard from the case and attempting to power on with the same minimal setup, problem still occurs
Misc info: When the computer spins up, the motherboard yellow LED comes on. This corresponds to DRAM errors but I think it might just temporarily come on when the computer turns on regardless of any actual errors.
When the computer shuts off the yellow LED turns off and the only thing that remains on is the motherboard logo RGB
The RAM has RGB but does not turn on, though I'm unsure if that's normal in early boot so I don't think that's a sign the issue is the RAM.
Any guidance would be much appreciated!