Problem:

The Login button at the landing page is not working. It shows service not configured when pressed.
Solution:
It may because of the Login service is not ready yet. ( not sure )
From Meteor doc,
Login service configuration is sent from the server to the client over DDP when your app starts up; you may not call the login function until the configuration is loaded. The function Accounts.loginServicesConfigured() is a reactive data source that will return true once the login service is configured; you should not make login buttons visible or active until it is true.
ref: https://devdocs.io/meteor~1.5/api/accounts#Meteor-loginWith%3CExternalService%3E