Unable to Get Access token to Orchestrator using API from Postman

For explicate features of Postman, I’d recommend setting the Authorization Type to OAuth 2.0 on the Collection/Folder and then have any subsequent requests within the collection inherit from the parent.

Its a bit cleaner and nicer to work with then say writing Post/Test Scripts so that the Authorization Request is run before other requests when needed or running the collection.

Another approach is to write a Pre-Script that mixes the use of Authorization on the Collection/Request that handles both the initial token and refresh tokens when the token has expired, or if you want to explicitly run an Authorization Request before another Request.