I just signed up yesterday. Once you sign up and get your DENTPIN you have to wait around a day and the ADA will send you another email saying you are approved then you have to wait 24 hours to sign up through prometric
This is what the ADA sent me after a day
"
Your application, XXXXXXX to take the Dental Admission Test has been processed. Your application is valid for one testing attempt and you are eligible to take the test between XX and XX.
Upon receipt of this email please wait 24 hours before scheduling an appointment. Your Eligibility ID is XXXXXXX (which is required to schedule a testing appointment)."
you can't just sign up for the DAT through the prometric website. First, you have to register through the ADA website, pay the outrageous fee, then they email you a eligibility ID.