I have the H270M-ITX and have installed a pci 1.0 4x card in the only pcie slot. When I go to system browser, it says the slot is empty and windows and linux cant see the card either.
The card lights up and is receiving power. I've set the pcie speed to gen1 and set the graphics to onboard instead of pcie.

I've also tested the network interface card in another computer with 0 issues