Resolution 1: Uninstall and re-install Office 365.
Resolution 2: If uninstalling and re-installing doesn’t fix the problem, try to uninstall office 365 first by following article:
Resolution 3: If the above method doesn’t resolve your issue, try performing Clean Boot on your computer and then reinstall. Follow these steps to restart Windows 10 in the Clean Boot mode:
To restart in Clean Boot follow the steps as per the following Microsoft Article:
https://support.microsoft.com/en-us/kb/929135