New RM850x won't send power

[CinnamonWombat]

I just bought a new rm850x to replace an ancient 850 psu I've moved from build to build for 13 yrs. Since I was going from a non-modular to fully modular psu, figured good time to upgrade case (diy pc > Crystal iCUE 465X) and cooling (stock amd > h115i RGB Platinum). Got everything torn down and built back up, had to rearrange to fans bit, new radiator doesn't fit on top of case. 

Pc was working perfectly fine an hour before I started swapping everything to the new case.

I've done the paper clip test, and it passed. I've checked all the pin connectors, and non seam to be loose. I've checked with both cpu cables the psu comes with, used different power cables, different outlets. Nothing.

The mb and psu standby lights don't power on, and there is a slight crackling sound when connecting the power cable to the psu.