Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
You only need your product key when you initially activate the Office licence, after that, it is a digital licence associated to your Microsoft account online.
1
Open Word.
At the top right of Word, log out of Office.
Restart (not shut down) your PC, then log back into Office, is your subscription then recognised correctly.
2
If not, log into your Microsoft account on this link, check the expiry date listed on your subscription, is that listed correctly.
https://account.microsoft.com/services/
If not, go to the Payments and Billing section, is it indicated your payment has been processed correctly.