When registering for a course, please verify that your credit card information is correct and up-to-date, and that the address entered on the registration page matches the address associated with your credit card.  If this is the case, and you are still unable to register, please send an email to [email protected] for assistance.  In your email, please be sure to indicate: the course(s) you are hoping to register for, the web browser you are using, and what error messages you have encountered.  This will help us to diagnose the issue.