This is either because you have not met all the pre-requisites for the course, or you left a past booking incomplete. First, return to the order by going to the home page and clicking ‘Continue with your order’ in the task list. Then scroll down and click the ‘Discard’ button. Now reattempt your booking. If you are still unable to continue, you may not have met all the pre-requisites for the course. Please read the red error messages at the top to see which courses you need to complete first.