XPS 8930, not recognizing M.2 SSD

For the type of M.2 SSD, the XPS 8930 will recognize and supports M.2 PCIe/NVMe solid state drive, not M.2 SATA SSD.  Verify which type of M.2 SSD you are using.

For the usage settings, M.2 slot can be used for NVMe SSD boot drive, storage drive.  SSD in M.2 slot can also be setup as accelerator cache for SATA HDD/SSD boot drive. 

If you are preparing for a Windows installation, you can check in BIOS settings and set SATA operation mode to AHCI to see if the system can detect the NVMe SSD in M.2 slot during installation process.

Good point - the M.2 NVMe drives are not recognized.

When I prepare to change SATA Operation from RAID On to AHCI I get a warning this may prevent the OS from booting or require a reinstall. I currently have Windows on an SSD connected via a SATA port. If I change to AHCI will that create a problem with the OS?

If you follow this process to change RAID to AHCI, it won't create problem to your current boot drive.  

https://support.thinkcritical.com/kb/articles/switch-windows-10-from-raid-ide-to-ahci

Thanks. I currently can't boot to Windows so can't use that process.

It would be a lot easier to disclose your goal and current issue than providing answer to each question that does not resolving your issue.  By changing RAID to AHCI you can't create problem to the OS because it is not working already.  No longer a valid concern.

In the case that your system boot drive is corrupted, replacing the boot HDD with an M.2 NVMe SSD is a good choice and good upgrade.  After installing new NVMe SSD to the M.2 slot, change RAID to AHCI and performing a clean Windows installation using USB drive created by Windows Creation Tool.