If you do a push-button reset of your PC to reset it to the manufacturer's initial configuration, the following two conditions might occur in Office after the reset:
Office prompts you to activate by displaying the Let's get started window with options to Try, Buy, or Activate Office.
Some Office apps, such as Outlook, Publisher, or Access, might be missing
To reactivate Office and reinstall any missing Office apps, please reinstall Office as described in Download and install or reinstall Office 365, Office 2016, or Office 2013 on your PC. When the Office install completes, Office will be activated, and any missing apps will be restored.