Hello Arjay Aldrich Bueno
"Some subscriptions types would be required to have sufficient history on Azure prior to creating an App Service Domain. Free trial and credit based subscriptions are not eligible to create an App Service Domain."
"Free subscriptions, which don't require a confirmed credit card, do not have the permissions to buy App Service domains in Azure."
It's suggested to Remove spending limit on your subscription-
https://learn.microsoft.com/en-us/azure/cost-management-billing/manage/spending-limit#remove
If the above steps won't help contact Azure support directly. Open a support ticket through the Azure portal.
https://learn.microsoft.com/en-us/answers/questions/1663421/the-subscription-(subscriptionid)-is-not-eligible
https://learn.microsoft.com/en-us/answers/questions/1629290/the-subscription-x-is-not-eligible-to-create-an-ap