@Kakooza-Allan-Klaus - Based on the limited information, I would be interested in what you have configured in the Authorization Tab, as you should not be setting anything there for the initial authentication.
In the method you have approached it, it is as simple as
I would also verify in the External Applications section of the Cloud Portal that you have copied your Client ID, Secret, and Scope details appropriately.
You could then take it the next step and using the Tests tab, capture the access_token from the response and use pm.environment.set to assign it to a Environment Variable for use in other requests when setting your Authentication as a Bearer Token.
Alternatively in Postman you can set the Authorization on a Collection or Folder to OAuth 2.0 and it will handle getting your auth token and when needed the refresh.
In other Requests you set the Authorization to Inherit auth from parent.
Yoichi
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jast1631
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