When an account is closed it can be for multiple reasons. If the account is restricted, it generally settles around verification of identity issues, as required by the Patriot Act and other bank regulations. However, having an account close and permanently locked/restricted generally revolves around other issues.
The most common are issues involving you or the people you that have sent you funds or you have sent funds to. When suspicious activity occurs (again, it maybe someone sending you funds or who you sent funds to), and a bank employee, not necessarily Green Dot, created a SAR report. Suspicious Activity Reports are investigated by FinCEN (Financial Crimes Enforcement Network) and results are sent to the involved banks within 30 days in most cases.
Banks are private business and there are various clauses within the terms and conditions you agreed to when you opened your Apple Cash account. The bank will close the account based on factors disclosed in the SAR investigation or clauses in the terms and conditions. Banks do not need to disclose reasons for their actions. You are not charged with a crime and the business chooses to not do business with you now or in the future.
That sounds harsh, but in my personal opinion, it’s a warning that when you open your next account, make different choices in how you use the account and read the terms and conditions so you know what your responsibilities and limitations are.