A family of Microsoft word processing software products for creating web, email, and print documents.
Urgh, this issue is ridiculous as it's a simple permission issue that just wouldn't arise in Linux (or at least would be easily rectified).
All my documents within one directory magically became read-only. Nothing I tried from the above suggestions seemed to work.
I'm using OneDrive for business with Win10 (latest versions of everything).
I had the idea of creating a new directory, cut and paste the documents into that and hey presto they worked again.
So I deleted the old (now empty) directory, renamed the new one to the name of the one just deleted... guess what, all the documents were read-only again.
So as a 'workaround' I have to add a suffix to the directory name (e.g. DNAME_) just to keep write access. The old DNAME seems to associate itself with being read only (although I can still write if I use O365 online via a browser, so it's a Win specific issue).
Sort this mess out!