Hi T,
Can you please check the Student account FAQ here and see if you match all the requirements for country location, subscription details etc - https://learn.microsoft.com/en-us/azure/education-hub/azure-dev-tools-teaching/program-faq
Also try to use another credit card if you have and if not try contact the support over here - https://support.microsoft.com/en-us/topic/global-customer-service-phone-numbers-c0389ade-5640-e588-8b0e-28de8afeb3f2
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