Intel Motherboards : NVME M.2 on Z170 Extreme 4 not working?

I just installed my first NVME M.2 SSD (Samsung PM961) on my Z170 Extreme 4 and it's showing some strange behaviour. I actually think it's faulty, but I'd like to make sure I set it up correctly first.

When I first started the computer with the new SSD, it was working fine in Windows (10). After a reboot, it disappeared. I tried a few things and updated the Bios to the latest version (7.00) and the drive showed up again, only to disappear again when I turned the PC on again later. No matter what I do now, I do not get the drive to work again, it doesn't even show in the device manager anymore. Interestingly enough, the PC takes a lot longer to boot now, even with Fast and Ultra Fast boot enabled.

If I'm not mistaken, an NVME SSD does NOT show in the storage devices list of the UEFI, only in the system browser overview? Mine doesn't show in either one.

I disconnected my system drive and started a Windows 10 installation to see if that sees my drive, but it doesn't either (with CSM set to UEFI or disabled completely).

So in my opinion, it's pretty obvious that the drive if stuffed, I just want to make sure I didn't miss anything crucial for an NVME device to work.

Thanks