As much as I love the Apple iWorks apps (Keynote, Pages et al), generally you should probably avoid asking your students to use these iWorks apps completely, and use their Google Docs equivalents instead. They don't have all the pretty bells and whistles, but it's much easier for you and for them, and I'm betting that the actual elements they've created that you are assessing have nothing to do with how funky the tech tool is. And Google Docs have a load of other features that are better for teaching and learning that the Works don't have the ease of access, commenting, collaboration and so on.
Otherwise you're faffing about with formats, versions, and of course it's very tricky to monitor their work via Hapara as the format is not web friendly... there are ways but they are fiddly...
Well the simplest solution is to ask them to change it to a Google doc. How?
Export it as a Microsoft format, eg Powerpoint, MS Word et al.
Move the MicroSoft version into Google Drive.
In the browser, select the MS version of the file, open with the relevant Google doc,
Keynote=GSlides, Word=Docs, Excel=Sheets (right click).
Done