Please check the release notes of January 6th under Pushnotifications.
If your app does not use pushnotifications you can use the automatic build in the cloud but you have to uncheck the Pushnotifications checkbox under Permissions.
If you do use pushnotifications you can not use the automatic build and you have to do it manually with phonegap.
The google-services.json file will be provided by Google when you set up your FCM project. Put it in the correct directory as indicated in the config.xml file of your phonegap package:
<resource-file src="config/google-services.json" target="app/google-services.json" />