The office program shows an unlicensed product message on it if the product is not activated. The program requires an official license key for activation. Here you can find some more issues.
Unlicensed Product and activation errors in Office 2021/2019
Firstly, sign in to Microsoft 365 or Office 2021/2019 with the right account. If Office asks you to sign in, enter the account you used to buy Office.
Secondly, check for multiple copies of Office.
After that, check your subscription status.
Finally, troubleshoot activation.