Here's where you can enter those product keys.
You'll see this error message if you enter a product key for a version of Office that isn't available for download from /setup. Sorry, we can't find this product key in our database (ERR_INVALID_TOKEN) or Sorry, we can't set up your account at the moment (ERR_MISSING_PARTNUMBER or ERR_PKPN_DETAILS_NOTFOUND)