I faced the same problem. when I used build.gradle (module.app) the version was different.
compile 'com.google.firebase:firebase-core:11.0.0' compile 'com.google.android.gms:play-services-auth:11.0.1'
Build> clean up the project I saw exactly the problem that was noticed when starting the project.
just fix the version and run the project
compile 'com.google.firebase:firebase-core:11.0.0' compile 'com.google.android.gms:play-services-auth:11.0.0'
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