401 Atter Google login

Please make sure you followed the last step in the instructions:

Once your Registered App has been created, you can go to the "Consent Screen" menu item to configure how your app approval dialog will look for users when trying to register using Google/Google+.

You'll need to set all the information on that page, which is what is shown when a user has to approve your application to login to your site.

I hope that helps, but if not, let me know.

Thanks,
Alex