A family of Microsoft word processing software products for creating web, email, and print documents.
UPDATE: There was a patch for Office today but it did not fix the problem for me (Office 2016, not 365)
I have been checking for updates to Office 2016 daily during this problem. There were patches to Office today and I applied them. I then opened a Word doc on OneDrive, made a change, clicked File then Save and I got the same popup. I was able to close (X), and save the file as normal. The pop-up has not gone away for my config.
Just in case: How to manually apply updates
Open an office app (e.g., Word) and create a new blank document (so you don't mess up a real doc). Click on File, then Account, then Update Options (button toward the middle of the screen), select Update Now. You will get a window showing update status. Note: If there are updates, you will have to close all Office Apps so be ready (including Outlook). This works for Office 2016 - someone with 365 can verify for that config.
No good results but wanted to let you know.
sf