Hi @Luis Fortes ,
There is a policy in place that requires sufficient payment history prior to purchasing a domain. Any subscriptions without sufficient payment history will not be allowed to purchase domains and will similarly receive error message you are getting per the documentation.
Note
Depending on the subscription type, a sufficient payment history may be required prior to creating an App Service Domain. If you have made payments and are still running into this error, you can contact support and provide proof of payments.
Once payment history has been validated, you will be allowed to create a domain. If you need further assistance in creating a support request, please feel free to comment down below.