fake-api-jwt-json-server | Fake API with JWT Authentication using json | Authentication library

I set up a fake json server (fake-api-jwt-json-server) taken from GitHub on my PC. Using url http://localhost:8000/auth/login, I am able to post to it successfully from Postman but when I tried from Visual Studio 2019, I got the error 'No connection could be made because the target machine actively refused it' (see error detail below). The same was the result when I tried another fake json server. In both cases, the url included 'http://localhost'. From VS, I am able to get responses from api endpoints that do not include 'http://localhost' with no problem. Why are the localhost api urls not working when I try them from VS? I have tried switching off my firewall.

The error message:-

jServerAGetAccessToken Source: Tests.cs line 27 Duration: 2.1 sec

Message: System.AggregateException : One or more errors occurred. (No connection could be made because the target machine actively refused it.) ----> System.Net.Http.HttpRequestException : No connection could be made because the target machine actively refused it. ----> System.Net.Sockets.SocketException : No connection could be made because the target machine actively refused it. Stack Trace: Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions) Task1.GetResultCore(Boolean waitCompletionNotification) Task1.get_Result() Tests.jServerAGetAccessToken() line 50 --HttpRequestException ConnectHelper.ConnectAsync(String host, Int32 port, CancellationToken cancellationToken) HttpConnectionPool.ConnectAsync(HttpRequestMessage request, Boolean allowHttp2, CancellationToken cancellationToken) HttpConnectionPool.CreateHttp11ConnectionAsync(HttpRequestMessage request, CancellationToken cancellationToken) HttpConnectionPool.GetHttpConnectionAsync(HttpRequestMessage request, CancellationToken cancellationToken) HttpConnectionPool.SendWithRetryAsync(HttpRequestMessage request, Boolean doRequestAuth, CancellationToken cancellationToken) RedirectHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) HttpClient.FinishSendAsyncBuffered(Task1 sendTask, HttpRequestMessage request, CancellationTokenSource cts, Boolean disposeCts) HttpMethods.PostWithKey(Dictionary2 url, StringContent postParamaters) line 92 --SocketException ConnectHelper.ConnectAsync(String host, Int32 port, CancellationToken cancellationToken)

And now my code:-