As the title says I have a x570 pro wifi motherboard, it has 2 nvme slots and while my first nvme shows up the second does not. I have reinstalled windows 10, updated to latest bios, looked into disk management (not there even after rescan), looked in bios (not there only see my first one) and device managers. (Nvme worked when testing on different motherboard so it should be okay), also reseated it a few times in the process.
Yeah I remember reading that if you use the second nvme slot you might go down to x8 instead of x16 for the pcie slot the gpu is in but I didnt see anything mention that you are not able to use the pcie slot then. (I am not totally well read in this subject however)