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.
Firstly, If the product key is used in more than allowed devices, it will show you unlicensed in the other devices. Unlicensed software cannot be used.
Secondly, you cannot edit the word files and save them. The unlicensed error message also appears if the payment is overdue for subscription-based products.