A family of Microsoft word processing software products for creating web, email, and print documents.
What happens when you try to sign in? Any error messages?
Do you have a license for the entire office suit or just word? If you only have word and office was preinstalled on the computer, you need to uninstall it and install just Word from your account.
Uninstall office from Windows Settings > apps > installed apps. Look for Microsoft 365 to find the subscription version. Click on it then click Advanced.