Exactly what was happening to me. Plug a DisplayPort cable into the motherboard and see if that works. For no discernable reason, doing that made the HDMI on my GPU start working too.

I was having the same issue, came here and had no success with anything listed and was ready to give up hope until my friend suggested trying the DisplayPort cable directly into the motherboard. Fixed the whole thing, even making the HDMI in my GPU w...