I absolutely LOVE Funnelish - spectacular! I'm having a hiccup setting up the Smart Optin for Google.
Per FB: As stated in the documentation, I setup dev accounts with FB & Google, and setup FB's OAuth redirect URI, which has a "/" at the end of the URL. I did not do anything with the Redirect URI to Check, and it works like a charm! However, they note this will change in March 2018 (you'll need to list all the URI's the login may come from).
Per Google: That being said, the Google is being a bit of a pain. When I created your OAuth client, I put in the regular domain without a "/" at the end (it errors if you do) and it requires all your "Authorized redirect URI's". I set it up with the page's URL, and it works until it's supposed to put the customer's email in the input form. Am I missing something on this step?