I need help trying to figure out what I am missing here. Running the API here brings back a response. 

So I copied the request body and the response body to the call and assigned all variables accordingly.

Now when i run the call during run-time, i hit a 400 bad request error when it gets to the API call... i have debugged and everything seems to get assigned correctly, I need a help figuring out what it is i am missing.

Have you tried changing the logging level on the api (in service center) and then see what actually gets sent? That is the route that I normally go.