x99p-SLI not detecting second GPU - "base system device" in device manager

[romandesign]

There is a broken device in Device Manager - shows up as "base system device", and in properties has "PCI slot 2 (PCI bus 4, device 0, function -). When I install second GPU in slot 2 - it's not detected at all. However in slot 3 it is detected and working, but the "base system device" is still showing. How do I fix that?

I would rather put the second card in slot 2, it has more lanes and there will be more room for air to cool the main GPU.

[dmdilks]

Look in Miscellaneous Settings and under PCIe Slot Configuration maybe you can change something in there.

Plus have you done this too:

When two or more graphics cards are installed, we recommend that you connect the SATA power cable from the power supply to the ATX4P connector to ensure system stability.