I have an old HP laptop running Windows 7. When I connect my TV with an HDMI connector I can see the second screen show up on the windows display settings. It even recognizes the brand and size of the TV. I can also see the "no signal" message on the TV disappear for a few seconds and then come back.
Any settings I choose at this point won't make anything show on the TV. I tried splitting the display, duplicating, or just using just the TV screen.
What else could I try?