An Office product key uses a combination of 25 letters and numbers in this format:
Product keys include hyphens, but you can omit them when you enter your product key.
You can sign in to activate Office 365, Office 2016, or Office 2016
If Office is prompting you for a product key, you can enter your Microsoft account instead. Try selecting the Sign in with an active account instead link in the Enter your product key dialog box and sign in with the Microsoft account that you associated with Office. We can help if you can't remember the Microsoft account you use with Office.
Note: If you're using Office Professional Plus, you'll need a product key to activate Office.
I can't find my product key
Here's where to get help with your product key:
Contact support about my product key
If you’ve followed the guidance in this article and still need help, visit our Microsoft support page for assistance.