Postasync works with UWP but breaks on android project

Been having issue with Xamarin Cross Platform Android Project. I am using Wep Api Project to call a service from xamarin portable project.

//Portable project
var auth = new SigninModel
{
Username = username,
Password = password
};
var stringContent = new StringContent(JsonConvert.SerializeObject(auth), Encoding.UTF8, "application/json");
var response = await Client.PostAsync("http://localhost:54019/api/AuthenticationApi/Login", stringContent);
//WebApi
[System.Web.Http.Route("api/AuthenticationApi/Login/")]
[System.Web.Http.AcceptVerbs("GET", "POST")]
[System.Web.Http.HttpPut]
public DBResult Login(AuthenticationModel model)
{
SupervisorModel result = null;
bool hasError = false;
string errorText = "";
if (ModelState.IsValid)
{
result = Authentication.AuthenticateUser(model.Username, model.Password);
}
else
{
hasError = true;
}
return new DBResult { status = !hasError ? "Success" : "Fail", descripText = BadRequest(ModelState).ToString(), data = new SupervisorModel { Id = result.Id, Name = result.Name, Surname = result.Surname } };
}