Bought a brand new, unopened RX 550X from Biostar. Put the card on motherboard Gigabyte GA-H77M-D3H (not sure what revision). No POST. Tested the card onto a B450 Aorus Elite, works like a charm. PSU - 600W AeroCool. GA-H77M-D3H works with Msi Armour 5500 XT 8GB. Not sure about the problem. Any ideas?