To verify your student status in Azure, you need to sign in using your school email address (typically ending in .edu). Since you mentioned that you have not signed in with your school email, this could be the reason for the verification failure. Make sure to create a Microsoft account using your school email if you haven't done so already. This account will allow you to access Azure and claim your student offers.
If you continue to experience issues, ensure that your school email is properly linked to your Microsoft account and that you meet the eligibility requirements for the Azure for Students program.
References: