Cybersource API "Create a Boarding Registration" Works on Developer Portal but Fails in Postman

Artan
Dabbler

Cybersource API "Create a Boarding Registration" Works on Developer Portal but Fails in Postman

POST https://apitest.cybersource.com/boarding/v1/registrations

I'm trying to use the Cybersource API for the "Create a Boarding Registration" feature, as documented here.

When I test the request on the Cybersource developer portal, it works perfectly. However, when I replicate the same request in Postman, I receive the following error:

{
    "response": {
        "rmsg": "{\"error\":\"UNAUTHORIZED_USER\",\"error_description\":\"UNAUTHORIZED USER\"}"
    }
}

I'm using the same headers as shown in the Cybersource documentation and portal:

 - Authorization: Bearer <Bearer> 
 - Content-Type: application/json
 - v-c-merchant-id: alpha_001
 - Host: apitest.cybersource.com

Has anyone else faced this issue or knows why this might be happening? Any guidance would be greatly appreciated!