If the appointment system notices that your activities are suspicious, it freezes your account for 72 hours. Once your account is frozen, you will not be able to log in for 72 hours. I assume that the following activities can trigger an account freeze - 1. Going into the appointment page too often on a given day. You will be shown a warning message if you have accessed the schedule appointment page too often - "You are approaching the maximum number of times you may view this page. Please complete your transaction at this time.” 2. Leaving the appointment page open in other tabs/browsers while you do other work. If your account is frozen, there is not much you can do. You will have to wait for a good 72 hours to be able to access your account again.