A family of Microsoft word processing software products for creating web, email, and print documents.
First, let's check whether your Office license and the Microsoft account signed in to Office match.
Sign in to your account here: https://account.microsoft.com/services. Can you find your Office subscription/license, and is it active?
If yes, open Word and go to File > Account. Is the same Microsoft account signed in there? Does the Office edition match your license?
If so, on the same page, sign out of your Microsoft account, then sign back in to see if that resolves the issue.
If you see a different Office edition than the one you actually own, look for the Switch License button on the same page and select the correct license.
If the issue persists, what exact error message do you get when you open Word?
Is the issue affecting only Word, or does it also affect Excel and PowerPoint?
Did you make any changes to your computer or subscription before the issue started?