1. If you are activating Office Professional Plus 2016 or Office Professional Plus 2019, you may be getting this error because you entered the product key directly at setup.office.com.
To activate this product, please make sure you are downloading Office from the Microsoft official link sent along with your key in My Orders of you could follow the Activation instruction How to Activate Office key.
2. If your product is neither of the above, please make sure that you are typing the key correctly and try again.
3. Try redeeming it at microsoft.com/redeem
However, if none of the above solutions work, please contact our Customer Support Team so we can check if you are eligible for a refund or replacement.
To assist you better, please include the details below:
1. Order / Transaction ID
2. Screenshot of the pop-up/error message ‘
3. Additional information (if any)