Error 400 when trying to test Example Sdk-Dotnet

I get an error (400) when I attempt to test SimpleTest example from Sdk-dotnet from this Link

on my machine (Windows 10 32bit 1909) Visual Studio 2015.

I followed all instructions.

Here is my App Console:

App Console

Here is the Code:

 

 // This loopback host is for demo purpose. If this port is not
        // available on your machine you need to update this URL with an unused port.
        private const string LoopbackHost = "http://127.0.0.1:52475/";

When I run the project I get this 

 

I click (N) or (Y) or (Enter), I get this

https://www.dropbox.com/oauth2/authorize?response_type=token&client_id=<MADE_IT_HIDDEN>&redirect_uri=http:%2F%2F127.0.0.1:52475%2Fauthorize&state=35d21a9368224dbcb2f61bb5d2705a74

I have IIS installed and working.

I registered the port 52475 and made sure it is unused, like this