Storage volumes appear only in Device Manager

[dp3drosario]

Hello Guys.
I'm having some issues with a recent PC I built for my boss. i7 8700, 16GB RAM, GTX1050ti.
The computer was originally built with 1 SSD and 1 HDD, and it worked perfectly. Windows 10 installed on the SSD with just a few other programs and some backup files were stored on the HDD.
Just a few days after it was built the owner decided he needed more storage so I bought another SSD and HDD for him, 4 in total, he installed and initialized the 2 new drives from Disk Management with no problems, then the 4 drives were formatted and accesible.
After a failed software installation, Windows was a bit corrupt (error messages popping up once in a while, in a fresh new build is unacceptable for me) so I suggested he reinstalled everything from scratch. According to the owner, the installation went smoothly, he formatted all the 4 drives on the Windows Installer, but when he logged into Windows the only available drive was the C: Drive (One of the SSDs, the one that originally had the OS on the first install).
So here is what I found out:

-The drives do NOT appear in Disk Management (Tried rescanning and everything).
-The drives do NOT appear as bootable drives in BIOS.
-The drives are NOT listed as disks with diskpart on the Command Prompt.
-The drives no longer appear in Windows Installation menu.

but..

-The drives DO appear under "Storage devices" in Device Manager.
-The drives DO appear under "SATA DEVICES" in BIOS.

The motherboard is Gigabyte B360m -DS3H.

I've been building computers for myself and friends for a long time and this is completely new to me.

Any suggestions? Thanks in advance!

 

[mdd1963]

delete them in device mngr, restart, they should be redetected...

Might have him do one at a time, perhaps one's read issues are dragging down the others....