akka PubSub not working across distributed system

Question

I have a system that is clustered deploy on k8s, it will have multiple instances when it's deployed. My code sample like below

import akka.actor.typed.pubsub.Topic
import akka.actor.typed.scaladsl.Behaviors
import akka.actor.typed.{ActorRef, ActorSystem}

object ClusterSystem extends App {
  private val logger: Logger = LoggerFactory.getLogger(getClass)

  ActorSystem(
    Behaviors.setup[Unit] { context =>
      implicit val system: ActorSystem[_]           = context.system
      implicit val ex: ExecutionContext             = system.executionContext
      implicit val clusterSharding: ClusterSharding = ClusterSharding(system)

      val pubSubRef: ActorRef[Topic.Command[Message]] = context.spawn(Topic[VendorData].  ("cluster-message"), "ClusterMessage")

      val publishService = new PublisherService(pubSubRef)
      val subscribeService = new SubscribeService(pubSubRef)

      Behaviors.empty
},
    "ClusterSystem"
  )
}

PublisherService:

import akka.actor.typed.pubsub.Topic

class PublisherService(pubSubRef:ActorRef[Topic.Command[Message]]){
   def publish():Future[Done]={
     for{
      _<- Future.unit
      _ = pubSubRef ! Topic.Publish(Message("someRandomData"))
     } yield Done
   }
}

SubscribeService:

import akka.actor.typed.pubsub.Topic
import akka.stream.typed.scaladsl.PubSub

class SubscribeService(pubSubRef:ActorRef[Topic.Command[Message]]){
   def subscribe():Source[Message, NotUsed]= PubSub.source(pubSubRef, bufferSize = 10, overflowStrategy = OverflowStrategy.dropHead)
}

What I expecting is I can get all the message from the subscribe API, but right now, I only can get the message that published on each node. Example: instance-1 published message : M-1, M-2 instance-2 published message : M-3, M-4 Expecting: connect to the instance-1's subscribe api, and I got message: M-1, M-2, M-3, M-4