I have a Asus Hyper M.2 X16 CARD V2 with (4) Intel 1tb ssd.
I have no problem installing Windows 10 on the computer and card.
So I decided to add (2) 1tb PCIe on the Motherboard itself because I wanted to install all my games on it… and now I can’t install Windows 10… It only sees the PCIe 1tb…and wants to make it my primary drive.
Remove the NVME in the m.2 slot and install on the 4xPCIe card and only then introduce the m.2 SSD. Did you install the 4x card with RAID mode enabled? This requires raid specific drivers at the point of install. Obviously you must have the boot priority correct and in any case only install with the drive/drives that you want windows on otherwise you can be left with the boot sector on a different disk than windows was installed on.