I saw someone with this exact same issue previously. I think this is the form factor officially supported.
https://www.newegg.com/Product/Product.aspx?item=N82E16820249086 (M'2 version) non-AIC
Your board doesn't have any PCIe x8 slots, But the card could probably run up to x4 in one of the x4 slots. I'd check to be sure it didn't affect graphics performance, or create another resource issue. Is your OS installed to this device? Were you able to select the UEFI: prefix during OS install? We've seen this affect disk performance previously. It may also be necessary to supply an AHCI driver via USB during install for the card to work optimally.
1 x PCI Express x16 slot, running at x16 (PCIEX16)
* For optimum performance, if only one PCI Express graphics card is to be installed, be sure to install it in the PCIEX16 slot.
2 x PCI Express x16 slots, running at x4 (PCIEX4_1 and PCIEX4_2)
3 x PCI Express x1 slots
(All of the PCI Express slots conform to PCI Express 3.0 standard.)