Intermittent ASP.NET oAuth issue with Google, AuthenticationManager.GetExternalIdentityAsync is returning null

Question

I am trying to fix an intermittent issue when using Google as an external login provider.

When attempting to login, the user is redirected back to the login page ra

Answer 1

Make sure that 3rd party cookies are enabled. I have found out that if you're not logged into google when you try to 'Register' a user with your application, it redirects to the login page as it looks for this cookie that isn't there, but still manages to do what it needs with the external provider. The next time you try to 'Register', because it's done part of the process it doesn't need to look for the external cookie anymore and so succeeds second time around.