Question Brand New PSU Failed

Jun 26, 2019
This will be a novice question because I am not experienced working with hardware. I attached as many details as I could. Just purchased a brand new ROSEWILL Gaming 80 Plus Gold 1200W Power Supply for my 4 GPU mining rig. I plugged it in with 0 cards to start and everything started up fine. Shut off the power with a screwdriver and the PSU switch, plugged in 4 GPUs and it had trouble booting saying "BI initializeLibrary failed 0xc00000bb" on black window. Shut everything off again, unplugged a single graphics card (3 still plugged in) and it started up no problem. I then installed a power switch which made the computer reboot sporadically. I detached the power switch to stop it from rebooting. Soon after, the board was lit up, but the CPU fan would not spin or the PSU fan. I removed the PSU and did the "paperclip test" with an external fan attached via molex connector. The first time I did the test, the PSU fan turned on and the external fan started spinning for a few seconds and then stopped. I turned off the PSU and turned it back on to try again and this time the PSU did not do anything. When I plug the PSU back into the board, the lights turn on, but no fans spin and nothing boots up. Is my PSU dead? Is my motherboard failing? Is my PSU not strong enough? Am I shorting something? Please help.
I think you did this somewhat backward.

Starting with no cards, then add one at a time and try them. Does it work with one card? If so, try to move on to two cards.. etc.

It would also help to know what exact GPUs these are that you're plugging into the board.

Also, what motherboard is involved?