When students log in to their student account at TotalRegistration.net and request to cancel an exam registration, their school's AP coordinator is notified of the request and will either approve or deny the request. You will see a Pending message at the top of the student's dashboard if the school's AP coordinator has not yet taken action on their request to cancel the registration (see below screenshot).
If you request exam cancelation and change your mind before the AP coordinator cancels the registration, you can click the "Cancel request here" link, as pointed out in the below screenshot.
It is up to the testing coordinator to act on the cancellation request. Students should contact their testing coordinator if they have any questions regarding a pending cancellation request or the reason a request was denied.