KentorIT, SAML2, Okta, MVC Authentication - login

Question

I am a newbie, I have setup my MVC application that will use okta for Authentication, trying to achieve using KentorIT, when the user isn't logged-In it redirects to Okta, and but Okta sent the response back, I am getting null in loginInfo object always.

public async Task<ActionResult> ExternalLoginCallback(string returnUrl)
{
    var loginInfo = await AuthenticationManager.GetExternalLoginInfoAsync();
    if (loginInfo == null)
    {
        return RedirectToAction("Login");
    }

I have put my POC code at below Git Location,

https://github.com/psharepoint10/MVC-okta-KentorIT

I think I am doing some small mistake in configuration/settings.

Any help appreciated.