I have an Asus desktop with a 1920x1080 monitor and a 1920x1080 TV/monitor connected to a GTX560Ti graphic board with 385.41 driver. I can only extend them, I can't duplicate them. There is no Duplicate option.
The same thing happens on my Asus 1920x1080 laptop when I connect it to the TV or a projector. It is an N56VM with nvidia graphic card also. Very inconvenient.
If I connect the desktop or laptop to a lower res monitor, the duplicate option reappears and I can duplicate them, or extend them.
I have an HP 1600x900 and a Dell 3200x 1800 laptop that will duplicate on the TV or projector.
How do I make the 1920x1080 duplicate on the TV or projector?

I think this is a function of Windows 10 v1703 but I can find no one else with a similar issue so maybe it is Asus.