If you get this on a site you have SSL running:
400. That’s an error.
The redirect URI in the request, https://sheruknitting.com/
, does not match the ones authorized for the OAuth client. Visit https://console.developers.google.com/apis/credentials/oauthclient/483332312407-v02gve3ufeh5dpe7jv1e49fjfe57g41e.apps.googleusercontent.com?project=483332312407
to update the authorized redirect URIs.
then go to your settings>advanced and look down for
encrypt login form and set to yes.
That solved it for me. Even though I had both http and https in the return API box in my Google credential.
Hope this saves someone an afternoon of angst.