I have the same problem . The same drive 970 EVO on NVME M.2 + adapter on PCI-E 16x slot. I have integrated gpu so I don't use any graphic cards on PCI-E.
I installed drive in first yellow slot.
Created windows 10 Pendrive UEFI (using rufus)
Set in Bios CMS disabled.
set secure boot (enabled - installed key - default keys from bios)
set Windows UEFI OS
Started from UEFI pendrive, Installer recognized my 970EVO. I changed in diskpart to GPT and left empty disk.
Selected disk in installer and clicked next.
Instalation finished and restarted.
After restart I removed my pendrive. but BIOS can't see my SSD .
I tried another option , CMS Enabled (set UEFI first )
set non windows UEFI os , disable secure boot , and started instalation from Pendrive (formated from rufus as windows MBR non uefi)
Installer recognized SSD installed windows . but after restart don't see the drive. 🙁
Third try: I inserted SSD into black PCI-E and set in setting x4 mode,
CMS disable, set Windows UEFI OS, secure boot - enabled (key installed from bios) . Do I have to prepare special pendrive (which include keys??? ) I still use rufus to create bootable pendrive + windows iso from microsoft (newest i think 1809) .
result is the same after restart I can't see drive to set as boot
What should I do ?