We have a detailed thread on similar issue related to Azure for students subscription here : https://learn.microsoft.com/en-us/answers/questions/119914/unable-to-get-azure-for-student.html
Please follow the steps provided in the thread above and let me know if you are still seeing the issues.
Summary:
Raise a New Support Request via Azure Portal, filling out all relevant details as asked on the page. Please ensure that, at a minimum, you provide Error code (the 715- number) and at least either of Transaction ID and Email that you used to log in (if there’s a log-in). Having either Transaction ID or Email is important to us, or we won’t be able to research them.
Please ensure that there is no Personally Identifiable Information (PII) (like passwords etc.) in request details
Expect an Email acknowledgement post submission with all Case details and Support Request Number. Our internal Teams would reach out to you to follow through further and provide a resolution as applicable
FAQ - https://azure.microsoft.com/en-in/free/free-account-students-faq/