When editing a PowerPoint file offline, changes are not saved to FYI.
You have gone offline, continued to make changes while offline, saved and closed the file and you are expecting the PowerPoint file to be automatically checked back in to FYI.
You need to open, save and close the file again when you are online. This will check the file into FYI.
Note: Our developers are working on an update that will mean any offline changes are auto synced automatically when coming back online.