How to change the Office or Outlook Product Key
How can I find out which license I’ve used for which computer and how can I change the key if needed?
While you could simply try one of your Product/License Keys and see if it gets accepted, it’s not a very sophisticated approach.
The correct way to determine or change the product key depends on your version of Office or Outlook. However, you do not need to completely reinstall Office for either version.
Note: Office 365 installations don’t require a license key as they activate automatically when you log on to Office with your Microsoft Account.