You can’t open Add-ins (files with .ppa or .ppam file extensions) in this version of PowerPoint.
PowerPoint Show files (.ppsx, .pps, and .ppsm) will not automatically open in Slide Show mode.
All other files types, except PowerPoint 97-2003 files (.ppt and .pps), are supported in this version of PowerPoint. These files open as read-only and can’t be edited.
