Omniauth-facebook keeps reporting invalid_credentials

Question

I am trying to implement omniauth-facebook as described in Railscast #360 and have run into quite a roadblock. When I click on the signin link, I get the desired popup aski

Answer 1

I've noticed that omniauth-oauth2 > 1.0.3 will cause a problem too, uninstalling higher version and keep omniauth-oauth2 1.0.3 solved the problem ..