Question MSI mpg x570 will not POST with known working gtx1070, gtx1080, POSTS and runs with old gtx560

Sep 16, 2019
Recently picked up a MSI mpg x570 Gaming Wifi board, and the system will not POST with either my EVGA 1070 SC, or my friend's MSI AERO gtx 1080 (both run just fine in his rig, and well as in my old p55a Gigabyte board.) It runs fine with my old EVGA 560 ti. I've tried everything I can think to do - clearing CMOS, flashing the BIOS to different versions, drawing a pentagram around it and sacrificing a chicken, etc.

Hardware is as follows:
MSI mpg x570 Gaming Wifi motherboard
ryzen 5 3600 running stock (tests fine under 4G burn test)
16G corsair vengeance rgb pro 3200 (tests fine under memtest)
CoolerMaster GX 750w PSU

EVGA 560 ti (runs just fine)
EVGA 1070 SC (will not POST)
MSI AERO 1080 (will not POST)

I had MSI support on the phone earlier, and they said "hmmm that's weird," and sent me a beta BIOS revision which I flashed to the mobo yet alas, did not help. The tech claims they're going to try to clone my build there and replicate the problem. I'm absolutely boggled at this point. Any ideas?
Thanks in advance.