There are only two endpoints to access the API services: one of PRODUCTION and the other of SANDBOX. While your application is being developed, always use the Sandbox endpoint, and change it to the Production one only when your application is approved, and if you have the production token. Here are the two endpoints that are used to access the API:

Do not forget to add the API version before the resource, for example: /api/v1, for version 1 of the API.