Help with Asrock Killer Z97X (6 GPU Rig)

Hi guys, I have an Asrock Killer Z97x mother board, which has 3 16x PCI-E and 3 1x PCI-E. I have a 6 gpus to plug in, they are Nvidia 1070s. I can get 5 of them to work. However, for the 6th one I am trying to plug in an Nvidia 1070 into the the first 1x PCI-E (the one closest to the CPU) using a powered riser. In BIOS, using the system browser tool, I can see that the motherboard recognizes the GPU, as it is highlighted in yellow, and says something like Nvidia Graphics Unit or something like that. However, when I boot into windows 10, the system does not recognize anything on that port. I have ruled out the graphics card and the riser as I was able to plug both into any other PCI-E port, and windows 10 recognizes it as a GPU. I have also ruled out that having GPUS plugged into other PCI-Es is messing with it because I unplugged all the other GPUs, and just used this one 1x PCI-E, but it didn't recognize.

I am using the default bios.
I changed the Gen settings for each of the 16x to Gen1.

Is my motherboard defect or is there some setting that I need to change to make this work? Or maybe update the bios (hesitant on that).