Really annoying problem... Trying to set up my rig

[GizmoOG]

Hello,
So I'm having a really weird issue whereas I can't get my computer to turn on when riser is connected. All I hear is a click and the PSU cuts the power. I ran two seperate 6 to 8 pins PCI-e cables from PSU, one powering the riser and the other powering the GPU. On the PSU I connected the cables onto 2 random available 6 pin slots, and the riser only used 6 pin so I didnt connect two of them (you can take seperate 2 pins), while the GPU is using all 8 pins. I have tried multiple different risers, cables and changed out that little board that goes into the mobo. I have 2x 1070's and I am trying to power a rx 570 on the riser on top of that. I tried unplugging those two gtx 1070's and using their power supply cables for the riser and the rx 570, and suddenly it works. I have no idea if it is the cables or what the hell the problem is, and it is driving me insane. I used all night trying to figure this out but I am no closer... If the cables are the fault why would they not work? Normal type 3, 6 to 8 pin...
https://i.gyazo.com/3daccb16ca66c8b726347709639e2b06.jpg
Here you can see how it looks. Appreciate the feedback!

[leonix007]

tried unplugging those two gtx 1070's and using their power supply cables for the riser and the rx 570, and suddenly it works. I have no idea if it is the cables or what the hell the problem is, and it is driving me insane.

try it vice versa, get the cables you use for the AMD and install it to GTX, if it doesn't work, you can throw the cables in trash bins. Lol, seriously its already faulty, if you're a techy guy you could check the wiring continuity with testers