Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Hello, thank you for reaching out to Microsoft Q&A.Have you tried redeeming your product key using a different web browser or an incognito/private browsing window, and if so, were you then able to redeem the key successfully?
https://setup.office.com/redeem/enter-key
Also, try clearing your browsing history, cache, and cookies in your web browser, and then redeem the product key again. If the product key is redeemed successfully, you should see the subscription listed under your Microsoft account here. -