You're signed in with a Microsoft account that doesn't have a license to use this app. Here are some things to check:
Check what products are listed on your Microsoft account
Using the Microsoft account that you used to buy Microsoft 365 or Office, sign in to the Services & subscriptions page of your Microsoft account dashboard. From the list of products, you should see whether or not Microsoft 365 or Office products are associated with this account. If you don't see any, but you know you have a Microsoft 365 or Office license, try signing in with a different Microsoft account.
Make sure you completed your purchase
If this was a new purchase that you began from within the app, from the online Microsoft Store, or from setup.office.com, it's possible you didn't go through all the steps needed to complete the purchase.
- For Microsoft 365 subscriptions You were on the subscription expired screen and started a purchase or renewal process but didn't complete the process, your new purchase didn't get associated with your Microsoft account. Be sure to complete all the steps of the purchase and then close and reopen an app (such as Word or Excel).
- Non-subscription versions of Office If you bought a one-time purchase of Office, such as Office Home & Student or Office Home & Business from the Microsoft Store, be sure to select Redeem now on the Thank you for your order page. When prompted, sign in with the same account that's shown on the We couldn't find your product page.
- You have a product key If your purchase came with a product key, but you haven't redeemed the key yet, select the option Enter product key. Next, enter the key that was included in your packaging or online receipt.
Home Use Program purchase
If you bought Office through the Home Use Program, you'll need to uninstall Office on this PC and then install Office through the Home Use Program (HUP).