That motherboard with 6x1070 word pretty much out of the box for me.  Start with 1 card.  Install windows.  Install drivers.  Add a gpu, boot computer, WAIT 5 MiNUTES even with an SSD!  I swear windows searches the entire globe for drivers even though you have them installed, so after 5 minutes check device manager and you should have 2 cards.

Repeat this process with each card.  Remember to WAIT after you boot, like an abnormal amount of time, sometimes after 5 minutes or so the new card will be recognized.  Each time you shut down and and a card and reboot it will take a bit to recognize it.

If something doesnt get recognized it is 99% your riser.  there is no QC on those risers and about 5-10% are just bad