Most likely, you're trying to log in with a user account different from the one you associated with your license. When purchasing on our site, you entered a user ID that we have associated with your license. You can see this used ID in the email we sent you after the purchase. Please compare that user ID to the one mentioned in the error you get when trying to log in. You either need to log in with the user account mentioned in the email, or you can change the user ID of your license from the account management page.