> But now I am unable to save the presentation, I've tried copying and pasting slides to a new presentation and that won't save either
Is there any error message when you saving this presentation? If so, you can take a screenshot and share with us.
Besides, does this issue occur with other new presenations created on your devices?
If not, I would suggest you save this presentation as: PowerPoint 97-2003 Presentation to have a check.
You can also close your PowerPoint app, open File Explorer > Click View > Deselect the Preview Pane option > Re-open File Explorer and open this presentations.
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