I am working with CyberSource pilot endpoints, how can I get around the 401 unauthorized when testing in Postman or our application?

Question

I am working with one of the Pilot endpoints trying to implement the new CyberSource recurring billing for a customer of ours.

I had a discussion with CyberSource late last year, and was provided the API reference link to these new endpoints. The API endpoint is https://apitest.cybersource.com/rbs/v1/subscriptions.

I noticed that when testing these endpoints in the API reference page, they would work and the subscriptions were created in our Sandbox account.

When testing this endpoint in our applications integration however, I am seeing a 401 unauthorized on each request. I see the same thing when testing in Postman, but not when testing directly in the API reference.

Is there something I need to include in the request header or otherwise in order to make these calls work?