If you find you're unable to save files or Microsoft Office is now asking to be activated please run Managed Software Center which can be found in your Applications folder in Finder or via your LaunchPad. 

This situation will occur if you're running macOS High Sierra or Mojave and have not checked for updates in 2-3 weeks or more. Please screenshot or make note of any changes in open Microsoft Word, Excel or PowerPoint documents and close all open applications before attempting to install any pending updates.