Hi,
Did you used it in the past or using one of your accounts and card details? Check the eligibility over here ms-azr-0044p
"We offer eligible customers USD200 in Azure credits (“Credits”) to be used within the first 30 days of sign-up and 12 months of select free services (services subject to change). This offer is limited to one Azure free account per eligible customer and cannot be combined with any other offer unless otherwise permitted by Microsoft."
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