Aurora R6 NVMe hynix 256GB SSD not detected by Windows10 installers

System Config: Aurora R6, Intel i7-7700k, Nvidia GTX 1080, hynix M.2 256GB NVMe SSD, samsung 850 EVO 250GB SSD, 2TB HDD

It has been 8 days since I purchased this system. The hynix NVMe SSD is no longer recognised by/visible to the Windows installer USB or Linux Live Bootable USB. Funnily enough, the BIOS can still see the drive in the Main tab.

Solution(definitely a fluke)

1. Added a Samsung 850 EVO 250GB SSD
2. Installed Windows 10 on it. NVMe drive still missing.
3. Enabled AHCI mode in BIOS using procedure linked in this guide.
4. Voila! NVMe drive is back from the dead.

Update #1:

While the NVMe drive is detected inside Windows(installed on 850 EVO), it is still not visible inside Windows 10 installer. I've tried both RAID and AHCI modes.

Update #2:

NVMe drive is not visible to the BIOS.

NVMe drive is not visible to Windows Installer USB

NVMe drive is visible to Disk Management from Windows installed on 850 EVO.

I've tried restoring BIOS settings to default. Resetting CMOS. Didn't help.

Update #3:

Changing Boot List option to Legacy has activated the NVMe drive.

It shows up as M.2 PCIe SSD: PC300 NVMe SK hynix 256GB-(S4) 185275945GB.

Update #4:

Dell sent me a replacement drive. This one is made by Toshiba. It is functional.

THNSN5256GPUK NVMe TOSHIBA 256GB