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
Nothing special, manual indicates that one pcie slot is lost if you use two m2 ports but I have tested (lastest bios) and it´s false for my board....

I have tried with M.2 pcie Adapter+SSD M.2 and a gpu on indicated manual lost slot and works.