How do I fix "the required index.xml file is missing?" when opening Pages documents?

I can't open any documents from my son's iPad. Error message: the required index.xml file is missing. How do I fix this error so that I can open his Pages documents? Before I ran the latest update as prompted when I opened Pages, I WAS able to open and view the document.

I did try restoring Pages using my Time Machine, but it still won't open the Pages document.

I have a brand new iMac that I just set up last week.

Son uses iPad at school, so we update when the school asks him to update. Will doublecheck his version of Pages but it should be pretty recent.

In general I don't like using Pages because it lacks a lot of the backwards / forwards compatibilty of Microsoft Word.

However, it is what my son uses with the iPad.

Most of the time I have to export his files as WORD files because we never seem to have compatible versions of Pages between the iPad and the desktop iMacs.

Where can I recommend that Apple improve its compatibility issues with Pages?

This week I am going to receive a new iPad at my school (I am a teacher) but I am 100% certain that it will not be compatible with the older version of Pages on my classroom iMac. I also avoid using Keynote for the same reason. I have 15 year old Power Points that I can still open, but I am hesitant to switch over to Keynote because I want to be able to open my files any time, any where.

Please advise.