array(0) {
}
HTTP Code: 404<br>Response: <pre>{
  "error": {
    "code": 404,
    "message": "Requested entity was not found.",
    "status": "NOT_FOUND",
    "details": [
      {
        "@type": "type.googleapis.com/google.firebase.fcm.v1.FcmError",
        "errorCode": "UNREGISTERED"
      }
    ]
  }
}
</pre>