[firebase] FCM getting MismatchSenderId

I had big trouble figuring out why I was getting a "MismatchSenderId" status. I added the gms dependency in the root build.gradle but my error was actually not applying the gms plugin in the app build.gradle.

If you have don't have this line in the app build.gradle, this could be the reason why the notification are not working: apply plugin: 'com.google.gms.google-services'