Message sent successfully: Array
(
    [error] => Array
        (
            [code] => 404
            [message] => Requested entity was not found.
            [status] => NOT_FOUND
            [details] => Array
                (
                    [0] => Array
                        (
                            [@type] => type.googleapis.com/google.firebase.fcm.v1.FcmError
                            [errorCode] => UNREGISTERED
                        )

                )

        )

)