I have intel HD graphics. the HDMI connection allowed me to view 720p on my full HD television via the HDMI connection. after i changed the resolution of the card to 1920x1080 there was no signal on the TV. even though i have now returned the HDMI resolution to 720p i cannot see anything on the TV. even though the TV is recognized by the system.
Did you try reinstalling the graphics drivers?
You can uninstall drivers by accessing Control Panel.
If you need to download latest drivers try below:
Did you try another HDMI cable?