I have a PowerPoint presentation that I created on my Mac and have moved (using iTunes File Transfer) to my 1st-generation iPad Mini running iOS 9.3.5. When I launch my Powerpoint app on the iPad, the presentation loads and runs just fine. I am signed in to my Office 365 account. However, I am having some strange problems with editing the presentation. Specifically, every time I open it I get the following notification:
Unsupported Content — Tap Save a Copy to edit a copy without this content.
(Of course the notification doesn't tell me anything helpful like what content is unsupported or even what slide it's on.)
If I don't tap "Save a Copy", I can view and present the slides, but apparently can't edit them.
When I tap "Save a Copy" I am prompted, as expected, to enter a new filename for the copy, and to choose where to save it (OneDrive, My iPad, Dropbox, etc.) But when I make those choices and click Save the app crashes and quits entirely.
I am also having trouble figuring out how (or even if) I can write/draw/highlight on my slides while presenting. If I swipe down from the top while presenting, a toolbar appears showing, from left to right, (a) a red X for exiting Slide Show mode; (b) a "Slide X of Y" indicator; (c) a greyed-out pencil icon; (d) a greyed-out pencil icon with the "gears/settings" icon superimposed on it; (e) a "mute screen" icon; and (f) an icon for entering Presenter mode, in which notes and thumbnails are visible.
Presumably the pencil icon is greyed out because the file is uneditable, because it contains unsupported content, which I can't identify or fix because the app crashes whenever I try to save a version without the content.
What, if anything, can I do? It may well be that the only answer is "convert to Keynote", which I am about to try, but it would be nice to get this thing working in PowerPoint if possible.