If the certificate already exists in Member Center, a “Your account already has a valid certificate” dialog appears. Typically, this happens when you move from one Mac to another. If possible, export your certificates as a developer profile file on the other Mac, and then import them on your new Mac, as described in Exporting and Importing Certificates and Profiles. If you don’t have a backup of your developer profile, click the “Revoke and Request” button when the “Your account already has a valid certificate” dialog appears.