SignalR One or more errors occurred

Hello,

I have downloaded SignalR from this site:

https://components.xamarin.com/view/signalr.

Code is presented below:

    var hubConnection = new HubConnection("http://192.168.1.4:57555/");

        var chatHubProxy = hubConnection.CreateHubProxy("TestHub");


        hubConnection.Start().Wait(); <---------- Here error appears


        chatHubProxy.Invoke("TryAddUser","elo").Wait();

I was trying to run the same code on UWP (here SignalR was downloaded from Nuget)
and it works correctly.
I could not find the solution in the Internet.