Web api windows authorization denied

Question

I want windows authentication in my web api, but I always get the following message: "Authorization has been denied for this request." Am I missing something?

IIS settings:

Web config:

Controller:

[HttpGet]
[Route("api/testauthentication")]
[Authorize]
public IHttpActionResult TestAutentication()
{
    return Ok(true);
}

Answer 1

Solution over here:

IIS Express gives Access Denied error when debugging ASP.NET MVC