Creating a Session using C# HttpClient

I am trying to create a session using c# code and am getting the weirdest error while creating a session (Note it does work through postman)

{"exception_body":{"http_response_code":401, "message":"No session exists.", "debug_message":"No session exists.","error_code":1000}}

Which is odd because I know the session does not exist I am trying to create it

Here is my c# code

            using (var client = new HttpClient())
            {
                client.BaseAddress = new Uri(baseUrl);
                client.DefaultRequestHeaders.Host = "dev.XXXX.cloud.opentext.com";
                client.DefaultRequestHeaders.Accept.Clear();
                client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
                client.DefaultRequestHeaders.Add("X-Requested-With", "XMLHttpRequest");

                var formConent = new FormUrlEncodedContent(new[]
                {
                    new KeyValuePair<string, string>("username", userName),
                    new KeyValuePair<string, string>("password", password),
                });


                HttpResponseMessage response;
                ApiResponse apiResponse = new ApiResponse();
              
                try
                {
                    response = await client.PostAsync("/otmmapi/v5/sessions", formConent);
                    var responseJson = await response.Content.ReadAsStringAsync();
....

I have tried with and without the Host, X-Requested-With and Accept Headers

Also I always get the same response whether or not the username and password is correct

It is returning the same error code as a GET but I confirmed it is actually doing a post

{Method: POST, RequestUri:
 'https://dev.****.cloud.opentext.com/otmmapi/v5/sessions', 
 Version: 1.1, Content: System.Net.Http.FormUrlEncodedContent, Headers:
{
  Accept: application/json
  X-Requested-With: XMLHttpRequest
  Content-Type: application/x-www-form-urlencoded
  Content-Length: 49
}}

It does not work using the javascript sample code, I get a Xorigin error when trying to run the same code

jQuery.ajax({    url : "https://dev.XXXX.cloud.opentext.com/otmmapi/v5/sessions", method: "POST",
   data: {"username" : "",  "password" : ""}}) 
   .done(function() { console.log("dfsaf")    })    
   .fail(function(req, res, data) {console.log(req, res, data)})