Mini Monitor 4K demanding extra power?

I've recently bought a Mini Monitor 4K that I ran for one job in my Mac Pro 5,1 with no issues. But when I plug it into my PC (well a Hackintosh, actually) the motherboard demands that I 'plug in PCI power to the graphics card' and refuses to boot or go any further.

Is this right? There's no power connection on the card, and it's a brand new Gigabyte Aorus Gaming 7 motherboard. The card is in the lowest PCIe slot - the 4x slot. I don't want to put it in the middle slot because that will knock my 1080ti down from 16x to 8x.

Should I be doing something in the BIOS to stop this and let the system proceed? Can't find anything about this online or in the manual.

I'm an idiot... mystery solved. When I installed the Mini Monitor 4K and closed the case the power cables to the main graphics card were fouled by the side of the case and it was that card that was demanding power not the MM4K. All good.