Since I don't have this issue with Microsoft documents, I have provided all of the suggestions I can in the link you provided. I noticed no one there confirmed that they had followed my advice about opening the problematic Word documents in LibreOffice Writer and then resaving them — before another attempt at opening them in Pages.
For Pages not opening Word .docx documents, they must be corrupted in some fashion by other software, and LibreOffice may be able to fix that issue. Or, the documents were dragged out of OneDrive while encrypted and not by using the OneDrive application to decrypt them before using Pages on them.