AuthenticationManager.GetExternalLoginInfoAsync() return null on Facebook

Question

I've developed an mvc 5 application and i use facebook login using External callback it was working well but now it is not working and i can't find out actual problem. And i find out why AuthenticationManager.GetExternalLoginInfoAsync(); is returning null value i used all most all the solution in my application but still have this problem. I remove session and set cookies but not effected.

I installed Facebook 6.4.0 from nuget to use FacebookClient to get user created events from facebook still it's working but i don't know what was happened know it's not working and returning null.

In Startup.Auth

app.UseCookieAuthentication(new CookieAuthenticationOptions
        {
            AuthenticationType = DefaultAuthenticationTypes.ApplicationCookie,
            LoginPath = new PathString("/Account/Login"),
            Provider = new CookieAuthenticationProvider
            {
                // Enables the application to validate the security stamp when the user logs in.
                // This is a security feature which is used when you change a password or add an external login to your account.  
                OnValidateIdentity = SecurityStampValidator.OnValidateIdentity<ApplicationUserManager, ApplicationUser>(
                    validateInterval: TimeSpan.FromDays(1),
                    regenerateIdentity: (manager, user) => user.GenerateUserIdentityAsync(manager))
            },
            ExpireTimeSpan = TimeSpan.FromDays(2)
        });
        app.UseExternalSignInCookie(DefaultAuthenticationTypes.ExternalCookie);

Set Facebook app id and app secret in Startup.Auth

app.UseFacebookAuthentication(
    appId: "my app id",
    appSecret: "my app secret"
 );

In login i use this below code.

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