The automated systems do not work properly and lock you out of doing what you need to do (credit card payments, exam registration).
The testing program will kick you out of your (paid for) test and not allow you to log back in or reschedule.
Customer service is unhelpful, if you call in (as you are forced to with some issues, the customer service is limited in what they can do) you get told that everything is down and they are unable to help you.
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