Failed: 415{"reason":"HTTP 415 Unsupported Media Type Request id: [ID].","message":"Applicationerror

Hello,
I am working on Microsoft ERP - Adobe Reader API Integration. I am struggling with passing MediaType in Request via programming.
I have followed Adobe Reader API Documentation and passing MediaType as per given example. But I am getting error when Request is sent via programming. The same works when I send Request using PostMan extension in visual studio code.
Snapshot 1 and 2 give information about Adobe Reader API Documentation.
Snapshot 3 and 4 give information about programming to send request and error that I am getting.
Snapshot 5 and 6 give information about sending request from PostMan and its response.
Any help or suggestion is appreciated.

Adobe Reader API Documentation

Request and Response from Visual Studio code programming

Request and Response using Postman extension in Visual Studio Code.