Rick ChurchillI want to show a KeyNote presentation on an external monitor and the presenter notes on my MacBook Pro.
I have connected the monitor via the HDMI port and it mirrors what is on screen and both showed the presentation. In System Preferences>Displays>Arrangement I then turned off Mirror Displays and now the external monitor is blank and the built-in shows the presenters screen.
The help instructions seem to imply that it should just work, the first line of which says
1. Connect an external display to your computer using a video adapter, or connect an Apple TV with AirPlay.
It worries me that the word “adapter” is used, surely it’s just a cable.
Where have I gone wrong?