Spawn() and late joiners

So as far as I understood from the documentation, the function Spawn should make that all late joiners also instantiate the object. But currently I can only make it work for players already connected to the server.

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4. using Unity.Netcode;
5.  
6. public class PrepareGameplay_Server : MonoBehaviour
7. {
8.     [HideInInspector] public int quantityOfRooms;
9.     [HideInInspector] public int decksPerRoom;
10.     [SerializeField] GameObject deckPrefab;
11.  
12.     void Start()
13.     {
14.         if (NetworkManager.Singleton.IsServer)
15.         {
16.             for (int i = 0; i < quantityOfRooms; i++)
17.             {
18.                 for (int j = 0; j < decksPerRoom; j++)
19.                 {
20.                     GameObject deck = Instantiate(deckPrefab);
21.                     deck.transform.SetParent(this.transform);
22.                     deck.GetComponent<Deck>().currentRoom.Value = i;
23.                     deck.GetComponent<NetworkObject>().Spawn(true);
24.                 }
25.             }
26.         }
27.     }
28. }
29.  

Am I doing something wrong here?