No type was found that matches the controller named 'something' MVC 5.2

I know there are already such questions, but the context there is very different probably because of the older .NET MVC versions.

I am getting the error No type was found that matches the controller named 'employee' when hitting the route "/api/employee/5" on the localhost. The entire route is like "127.0.0.1:8080/api/employee/5". The home route at "127.0.0.1:8080" works as expected.

I have configured the route in my controller.

EmployeeController.cs

[Route("api/employee")]
public class EmployeeApiController : Controller
{
    [HttpGet, Route("api/employee/{id}")]
    public ActionResult GetEmployee(long id) 
    {
        return Content(
            new Employee("Bobby", "Smedley",
                         "London", "Teheran",
                         EmployeeGender.M,
                         DepartmentCode.D_2157020,
                         "12345678901").ToString(),
            "application/json");
    }

}

I made no changes to the WebApiConfig.cs and it looks like follows.

public static class WebApiConfig
{
    public static void Register(HttpConfiguration config)
    {
        // Web API configuration and services

        // Web API routes
        config.MapHttpAttributeRoutes();

        config.Routes.MapHttpRoute(
            name: "DefaultApi",
            routeTemplate: "api/{controller}/{id}",
            defaults: new { id = RouteParameter.Optional }
        );
    }
}

Does anyone know what is the issue with that?