Try the function key to see what happens. On my Asus it's Fn+F8.
I have an ASUS Q500A laptop and an Insignia TV. When I try to connect the laptop to either one of the TV's two HDMI ports, there's no sound or display. I've made sure to try multiple cables and both of the TV's ports, choosing the 'duplicate display' option, and many other methods but no luck. It worked before but suddenly doesn't and I can't figure out how to fix this.