ASP.NET MVC areas return blank view

I have one ASP.NET MVC application which also has areas in it.

For short URL I have set route all actionmethods with short URLs in RouteConfig of areas like below.

//admin dashboard having short URL admin/dashboard
context.MapRoute(
            "admin_dashboard",
            "admin/dashboard",
            new { area = "admin", controller = "admin", action = "dashboard" }
        );

//student list having short URL admin/studentlist
        context.MapRoute(
            "student_list",
            "admin/studentlist",
            new { area = "admin", controller = "students", action = "List" }
        );

//new student having short URL admin/student/new
        context.MapRoute(
            "student_new",
            "admin/student/new",
            new { area = "admin", controller = "students", action = "RegisterStudent" }
        );

//edit student having short URL admin/student/id
        context.MapRoute(
            "student_edit",
            "admin/student/{id}",
            new { area = "admin", controller = "students", action = "RegisterStudent" }
        );

As you can see I have defined short URLs for all the actionmethods and it is also working fine except the last two which have calling the method but returns blank view.

        [Route("admin/student/{id}")]
        [Route("admin/student/new")]
        public ActionResult RegisterStudent(string Id)
        {
         ....mycode
         return View("RegisterStudent", mymodel);
        }

The problem is it is calling the method without any error, but it is not returning the view. It returns the blank view. Why does this happen, did I make any mistake?

If your request is going to your action method, then there is no problem in routing. If your action is returning a blank View then, there must be some problem with View itself.