4th card prevents computer from booting

Hey all.

Somewhat new to mining and although I've figured out some items myself, I cannot figure out why my computer won't boot after a new card.

In short, I'm running a Z170i Pro Gaming Mini ITX Mobo. Downside: it was 1 16PCIE slot and no 1's. So I bought a "splitter" and 4 risers. Two cards wouldn't work but I managed to discover through research that I needed to change some BIOS settings. Changing PCIe16_1 Link Speed, DMI Max Link and PCIe Speed from Auto to Gen 1 or 2 worked perfect. 3 cards ran without issue.

Picked up a 4th card recently and I just get a blinking cursor in the top left when trying to boot. I've swapped different cards and risers etc and they all work fine, it's only when any 4th card is connected.

Any ideas or suggestions?