Executing a GET using cpprest returns a 405

I have a URL which checks for the existence of a thing(https://thingworx-mvp.xrite.com/Thingworx/Things/thingName) which is issued as a GET from a c++ class using cpprest. The response is always a 405 from the cpprest class, however, when I execute the URL from Postman, a 200 is returned. Using a browser(chrome) also returns a 200 after asking for authentication.

The request headers from cpprest and Postman are identical. I have come across a few examples of people having similar issues and saying that you should replace the GET w/a POST. I tried that but received a 400 from the cpprest implementation and a 405 from Postman.

Why would the cpprest implementation return a different  result than Postman if the URL and request headers are identical?