Question samsung 980 m.2 issue

[Fenix1984]

So last night I helped my nephew with his first PC build. he picked all the parts and we put it all together. the issue comes with the m.2 drives. he bought 2 samsung 980 pro 2tb m.2 and we are installing them into a asus z790 hero through the hyperdrive PCI. the problem is only one shows up anywhere. bios and windows. I changed the setting in bios to dual for the PCI and same result. both work as we tested each alone and it showed right up but when using both only one appears. I remember this similar issue some years back on a build using 2 of the exact same sata drives but don't remember how we got it to work. any help appreciated.

 

[SkyNetRising]

he bought 2 samsung 980 pro 2tb m.2 and we are installing them into a asus z790 hero through the hyperdrive PCI.
the problem is only one shows up anywhere. bios and windows.

What is "hyperdrive PCI"?
Can you provide link to the product?
Did you mean this one?

ASUS Hyper M.2 X16 PCIe 3.0 X4 Expansion Card​

What slot did you install it in?
Third PCIE x16 slot on motherboard supports x4 mode only.
If you install ASUS Hyper M.2 X16 in it, then only single M.2 drive is supported.
Each M.2 drive requires x4 connection. So 2 drives will require at least x8 connection.

Anyway - motherboard has 3x onboard M.2 slots.
Use those instead.