Hey jstef.  Just got 13 of these from Holy the other day and, first off, they look great.  With that said, having mixed success thus far... working on getting them installed and only 1 of 3 are allowing Windows to recognize the attached GPU.  FYI, I have confirmed the riser itself is working by unplugging from your m2 and plugging directly into motherboard (Windows recognizes then).

Motherboard = ASUS Prime Z270-A

All other hardward & bios settings are the same.  Any ideas what I can try?  Thx!!!