UNet MatchMaker only works on LAN

Hi all!

I'm currently following one tutorial from Brackeys that use HLAPI from UNET, its the Multiplayer FPS Tutorial.

At some point, we implement a RoomList script and a Join system.

It works perfectly at LAN, but when I send it to someone on the internet, I can't see the room who their created.

Here is the code from JoinGame script.

The response callBack is successed, but the list is empty. I can't see rooms created from people outside my network lan. Any ideas ?

 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.UI;
 using UnityEngine.Networking;
 using UnityEngine.Networking.Match;
 using System;
 
 public class JoinGame : MonoBehaviour
 {
     List<GameObject> roomList = new List<GameObject>();
 
     [SerializeField] GameObject roomListItemPrefab;
     [SerializeField] Transform roomListParent;
     [SerializeField] Text status;
     private NetworkManager networkManager;
 
     void Start()
     {
         networkManager = NetworkManager.singleton;
 
         if (networkManager.matchMaker == null)
         {
             networkManager.StartMatchMaker();
         }
 
         RefreshRoomList();
 
     }
 
     public void RefreshRoomList()
     {
         ClearRoomList();
         networkManager.matchMaker.ListMatches(0, 20, "", false, 0, 0, OnMatchList);
         status.text = "Loading...";
     }
 
     public void OnMatchList(bool success, string extendedInfo, List<MatchInfoSnapshot> responseData)
     {
         status.text = "";
 
         if (!success)
         {
             status.text = "Couldn't get room list";
             return;
         }
 
         responseData.ForEach(match =>
         {
             GameObject _roomListItemGO = Instantiate(roomListItemPrefab);
             _roomListItemGO.transform.SetParent(roomListParent);
             RoomListItem _roomListItem = _roomListItemGO.GetComponent<RoomListItem>();
 
             if (_roomListItem != null)
             {
                 _roomListItem.Setup(match, JoinRoom);
             }
 
             //as well as setting up a callback function that will join the game
             roomList.Add(_roomListItemGO);
         });
 
         if (roomList.Count == 0)
         {
             status.text = "No rooms at the moment";
         }
     }
 
     public void JoinRoom(MatchInfoSnapshot _match)
     {
         Debug.Log($"Joining {_match.name}");
         networkManager.matchMaker.JoinMatch(_match.networkId, "", "", "", 0, 0, networkManager.OnMatchJoined);
         ClearRoomList();
         status.text = $"Joining {_match.name}...";
     }
 
     private void ClearRoomList()
     {
         roomList.ForEach(item =>
         {
             Destroy(item);
         });
 
         roomList.Clear();
     }
 }