I keep getting same error while trying to login with my Google account to Sharepoint through ACS.
I followed this tutorial: "http://www.fusecollaboration.com/blog/using-google-to-authenticate-with-sharepoint-2013".
The error message I'm getting:
It's not really useful, does anybody have some experience with this error?
As it turns out, I had to enable Google+ API. This is the post that helped: OWIN's GetExternalLoginInfoAsync Always Returns null.