Azure for Students: "You're not eligible for an Azure free account" after successful academic verification

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Scenario I am trying to activate the Azure for Students offer with a personal Microsoft account. Academic verification completed successfully (the page showed "Verification complete!" and I received the verification email), but the sign-up fails at the final step with "You're not eligible for an Azure free account." The message gives no reason.

Environment

• Personal Microsoft account (not a work or school account)
• School email from a partner university used for verification
• Chrome, tried in a regular and an incognito window
• This is a new Azure account: I have never used Azure, the Azure free trial, Azure for Students or GitHub Education with it. The account has no subscriptions, and the Azure portal shows only the default directory.

What I tried

1. Signing in through the university tenant failed with AADSTS90072, because my personal account does not exist in that tenant. I signed out and used the personal account.
2. Signing in with the university work/school account gave "Unable to confirm your University ID."
3. Academic verification then succeeded.
4. The address step first failed ("We couldn't validate your address"). I corrected the address format and it passed.
5. The sign-up then failed twice with "You're not eligible for an Azure free account."

What I suspect

• My phone number is correct, but it is pre-filled in an unusual format (national format with a leading zero, no country code) and cannot be edited on the sign-up page. I do not know whether this affects the eligibility check.
• The academic verification may be tied to a different session or account than the one used in the final step.

Question What are the possible reasons for this error after a successful academic verification, and how can I find out which one applies? Is there a way to edit the pre-filled phone number on the sign-up page?

(Screenshots attached with all personal details blurred)student-subscrption-error.pdf