Redirection to okta login page after logout not working

Currently our app uses okta login page .After logout we need to end the okta session and redirect them back to okta login page.After logout we are invoking logon method and from that logon method we have checked user authentication .if user not authenticated we just redirect to okta login page like below.But its redirects the user to okta dashboard page.Can anyone answer this question?

    [Route("LogOn")]
    public ActionResult LogOn()
    {
            if (!User.Identity.IsAuthenticated)
            {
                return Challenge(OpenIdConnectDefaults.AuthenticationScheme);
            }
            else
            {
                return RedirectToAction("DefaultAction","DefaultController");
            }

}