Firebase Web Codelab FriendlyChat - Google Auth Error

Working through the FriendlyChat Demo in the Firebase documentation for web http://ift.tt/27DZj2a and I am not able to authenticate against Google.

I'm using the web folder of the sample repo http://ift.tt/1TROsKW and I've modified the index.html to run locally instead of from Firebase hosting (following the instructions here: http://ift.tt/29zkUUb - basically replacing the server side scripts + init with ones that will run locally) and using firebase CL tools to serve it up on localhost.

Page comes up with "Sign-In with Google" target and when I click on it, it pops up a blank page and then eventually comes back to the main page leaving errors in the console.

Using latest code from the repo and v4.1.3 of Firebase

** Errors in the JavaScript console **

Uncaught Error: Network Error at firebase-auth.js:161
code: "auth/network-request-failed"
message: "A network error (such as timeout, interrupted connection or unreachable host) has occurred."
__proto__:Error

friendlychat-XXX.firebaseapp.com/__/auth/iframe?apiKey=XXX-…XXX&parent=http%3A%2F%2Flocalhost%3A5000&pfname=&rpctoken=XXX 
Failed to load resource: net::ERR_CONNECTION_TIMED_OUT