Bahktra

I was having the same issue with the motherboard seeing only 7 slots in bios and 7 cards in windows BEFORE i even installed ANY drivers. Firstly i installed the wrong drivers but then used DDU and after restart it still only showed SEVEN cards.
Now i managed to pinpoint another problem. When i have a card connected to the main pciE slot i get a black screen. Switching to the onboard graphics gives no image either and i CANNOT access bios.
I think the board is faulty. Going to return it today.

Will see what they tell me at the shop.