So i have i7 4770k a Maximus VII Hero and a CX750M psu. I am trying to run 3 of the GTX 1060s

2 is running directly on the motherboard

I am trying to run 1 gpu on the riser.

On the riser where i have 1 gpu connected The gpu fans spin on the riser but the gpu is not picked up/detected on the pc/motherbord.

If i plug in just the riser alone and no other gpus the riser works and outputs video.

I have tried 4 risers all do the same different brands of risers as well were tested.

Any ideas? Thanks all info appreciated.

Please see pics of risers and setup here.

https://imgur.com/a/qtsqE