clientscene.unregisterPrefab dosen't work?

Hi, I'm creating a card game , what i do need now is to distribute the cards on the players on the network here is the script that i developed which is attached to the player prefab :

 [System.Serializable]
 public class ToggleEvent: UnityEvent <bool>{}
  
 public class Player : NetworkBehaviour {
  
  
 [SerializeField] ToggleEvent onToggleShared;
 [SerializeField] ToggleEvent onToggleLocal;
 [SerializeField] ToggleEvent onToggleRemote;
  
  
  
 List<GameObject> Cards,EightCardsReceived ;
 List<Transform> startPositionsTransformList;
 List<Vector2> startPositionsList;
  
  
  
  
 public override void OnStartServer(){
    distributeCards ();
  
  
 }
 IEnumerator Mycoroutine (){
    yield return new WaitForSeconds(10f);
    Debug.Log (ClientScene.ready+"  Clientscene ready");
    if (ClientScene.ready)
        RpcdistributeCards ();
 }
  
 [Server]
 void distributeCards(){
    StartCoroutine ("Mycoroutine");
  
  
 }
 [ClientRpc]
 void RpcdistributeCards(){
  
    EightCardsReceived = PickUpCards ();
  
    if (isLocalPlayer) {
  
        for (int j = 0; j < 8; j++) {
  
            Vector2 cardPosition = positionCalculator (j);
            Instantiate (EightCardsReceived [j], cardPosition, Quaternion.identity);
        }
    }
 }
  
 void Start()
 {
    EnablePlayer ();
  
  
 }
  
 void DisablePlayer()
 {
    onToggleShared.Invoke (false);
    if (isLocalPlayer)
        onToggleLocal.Invoke (false);
    else
        onToggleRemote.Invoke (false);
  
 }
  
 void EnablePlayer()
 {
    onToggleShared.Invoke (true);
    if (isLocalPlayer)
        onToggleLocal.Invoke (true);
    else
        onToggleRemote.Invoke (true);
 }
  
 Vector2 positionCalculator (int J){
    Vector2 finalPosition;
    Vector2 currentStartPosition = gameObject.transform.position;
    Vector2 Increment = new Vector2 (1.41f, 0f);
    finalPosition = currentStartPosition + J * Increment;
  
    return finalPosition;
  
  
 }
 List<GameObject> PickUpCards (){
    List<GameObject> EightCards = new List<GameObject>();
    NetworkManager netM = NetworkManager.singleton;
    for (int i = 0; i < 8; i++) {
        GameObject currentGameObject = netM.spawnPrefabs [Random.Range (0, netM.spawnPrefabs.Count)];
        ClientScene.UnregisterPrefab (currentGameObject);
        Debug.Log (i);
        Debug.Log (netM.spawnPrefabs.Count);
        EightCards.Add (currentGameObject);
  
    }
    return EightCards;
 }
 }
 

In the console i get that the count of registered spawnable prefab dosen't decrease so clientscene.unregisterPrefab isn't working.

I appreciate any help . Thanks for reading.