Which software do you use to overclock more than 8 GPU under Windows 10 64bit fall update? Afterburner seems to be stuck at 8. Other tools even less.
Try with NvidiaInspector. The only problem I have is that I can not load saved profiles so I use MSI AB and additional overclocking programme( in my case as I have Zotac cards-Firestorm). WIth msi I oc 8 cards and with Firestorm 2 remaining. But Nvidia Inspector is able to detect >8, so if you are able to load saved profiles that will perfectly work.