While presenting a PowerPoint 2011 slide show from a MacBook during a videoconference, you may encounter a problem with the projector displaying a black screen in spite of having the resolution set to 1024x768 and the laptop display set to duplicate.
PowerPoint 2011 for Macs introduced what is called a ‘Ribbon Toolbar’ which contains ‘Setting options for Two Displays’. To access the ribbon click on ‘View’ along the very top of the PowerPoint Menu Bar then make sure the ‘Ribbon’ in the dropdown is ticked.
The Ribbon Toolbar opens up below the PowerPoint Main Menu Bar. Locate the ‘Setting for Two Displays’ option to the far right of the Ribbon Toolbar and select the ‘Mirror Show’.
Start the slideshow from this point and it will display both on the MacBook and on the projector screen.