Hey @sBalasubraman happy to hop in and help here. This is an intersting problem and could be a number of issues. I see you are using Postman to run this request, lets check something first to make sure its not an easy problem to solve.
First, can you run this request to the API without specifying parameters?
My initial thought is your authorization headers may be incorrect. Running without the paramaters can help us narrow down the problem for you! Lets start there and I will monitor this thread to assist as we test together! Looking forward to solving this for you.