Like Gate and Like Gate Pro plugins both, in order to work, they require a Facebook App ID. The plugins used one of the app IDs internally that’s why you didn’t have to enter one. With the latest changes with Facebook a facebook app can run on only one or two domains max, therefore using our Facebook App no longer works because we could set it up to use our domains. Now, we have to ask you to create a Facebook app for each of the sites that you intend to use our Like Gate plugins. If things change we’ll gladly remove the requirement of App Id.