I have same asus motherboard with 11 card using 2 m.2 to pcie and and pcie 4x splitter.
I have test same spliter and m2 adapters on msi gaming m7 without flaws
Last official firmware and Windows 10 on both.
MSI Z170A Gaming M7 ?!
One of the 2 m.2 adapters won't work on this board actually. There is a point in the manual which says something about the m.2 slot in combination with PCIe slot.
Furthermore the latest bios also doesnt work for me. I have to use an old one.
Please explain what exactly you did.
Best regards,
Mr.ARgful