ChatBehaviour.OnStartAuthority()': no suitable method found to override.

I am following a tutorial by dapper dino about using mirror chat system.(

) I followed to end but there is an error Assets\Chat\Scripts\ChatBehaviour.cs(14,26): error CS0115: 'ChatBehaviour.OnStartAuthority()': no suitable method found to override. I am using unity version 2021.2

Code (CSharp):

1.  
2. using Mirror;
3. using System;
4. using TMPro;
5. using UnityEngine;
6.  
7. public class ChatBehaviour : MonoBehaviour
8. {
9.     [SerializeField] private GameObject chatUI = null;
10.     [SerializeField] private TMP_Text chatText = null;
11.     [SerializeField] private TMP_InputField inputField = null;
12.  
13.     private static event Action<string> OnMessage;
14.  
15.     public override void OnStartAuthority()
16.     {
17.         chatUI.SetActive(true);
18.  
19.         OnMessage += HandleNewMessage;
20.     }
21.  
22.     [ClientCallback]
23.     private void OnDestroy()
24.     {
25.         if (!hasAuthority) { return; }
26.  
27.         OnMessage -= HandleNewMessage;
28.     }
29.  
30.     private void HandleNewMessage(string message)
31.     {
32.         chatText.text += message;
33.     }
34.  
35.     [Client]
36.     public void Send(string message)
37.     {
38.         if (!Input.GetKeyDown(KeyCode.Return)) { return; }
39.  
40.         if (string.IsNullOrWhiteSpace(message)) { return; }
41.  
42.         CmdSendMessage(message);
43.  
44.         inputField.text = string.Empty;
45.     }
46.  
47.     [Command]
48.     private void CmdSendMessage(string message)
49.     {
50.         RpcHandleMessage($"[{connectionToClient.connectionId}]: {message}");
51.     }
52.  
53.     [ClientRpc]
54.     private void RpcHandleMessage(string message)
55.     {
56.         OnMessage?.Invoke($"\n{message}");
57.     }
58. }
59.  

 

oops, wrong video

i mean this video, maybe

 

just use NetworkConnectionToClient instead of NetworkConnection and the problem should be solved.
public override void OnServerAddPlayer(NetworkConnectionToClient conn){}

 

Its a monobehaviour, not NetworkBehaviour