Why is User.Identity.IsAuthenticated not true after GoogleAuthentication?

I'm trying to debug an issue with OWIN and GoogleAuthentication, everything works on the redirect to google and then google redirects back and my custom GoogleAuthProvider is called and then finally a redirect occurs back to the desired page.

Unfortunately after the redirect back to the desired page,

!User.Identity.IsAuthenticated

is false so my account controller assumes that it needs to redirect back to google for authentication. My

GoogleAuthProvider.Authenticated(GoogleOAuth2AuthenticatedContext context)

function is called, and if it appears that the current user is authenticated before the redirect.

What can cause a user to become unauthenticated on a redirect? Why isn't the app setting or reading the authentication value between requests?

Stack Overflow link