I have 8 of these boards. I noticed something that maybe will help you. Sometimes when I restart the system it starts with less than maximum nr of video cards and is random, 5 cards, 7 cards. in order to bring them all online i have to take out the battery from the bios, then put it back in and afterwards it starts with 13 cards everytime.
It can see all the cards. The problem is that when I run the miner with 7 or 8 cards, the gpu threads randomly hangs. With 6 cards it works stable. Yesterday I swapped the board ( I have few of these) and still getting the same issue.