Forbidden schema creation

i am following the documentation to Create a schema, but it responds with 403 forbidden (i am including the Api-Token header), so i decided tu test the Create an event endpoint, and it works!! i am losing my mind over this as i do not see the issue, and i will appreciate every single response

Are you using a standard ActiveCampaign account or a developer sandbox account? Sandbox accounts have permission to create Custom Object schemas, and Enterprise plan customers can create private schemas. If you plan to create an app or integration for the ActiveCampaign marketplace, you can request a free developer sandbox account.