Postman isn't a web application and so won't do CORS.
As the message on the screen will be telling you - you need to accept the certificate your gateway is using before CORS will be processed correctly by the browser.
CORS is not something we have any control over - its part of the browser security framework.
Also make sure your API has CORS enabled in it, and you do not have any OPTIONS methods in your API as they will conflict.
------------------------------
Chris Dudley
------------------------------