Second display not able to run as a duplicate

Hello,

I have a laptop with an add on screen which I have run as a duplicate (ie don't use my laptop screen). The scenario has changed for some reason to two screen (extended) mode where I can use both at one time. I want to chnage back to the one add on screen. I have tried the display maintenance screen to firstly turn off the extension option on the add on screen. Then I used the duplicate option - move the 1st screen over the 2nd screen and still doesn't work.

Any ideas? Thanks