The motherboard will try to output video to either the onboard or the discrete card, depending on BIOS settings. Power it on and try both (or all if more than 2) outputs.
If you can't find working video, reseat the card and power connectors; if there are more than one PCIe power connector on the card, make sure to hook up power to all of them. Try to find video again.
If still nothing, verify that everything (monitor, cable, etc) works with the old card, and RMA the 570.
Can you link to the exact card model?