EntityNotFound (21404) Error at ApproveBackfillTicketAsync

there is error while trying

await MatchmakerService.Instance.ApproveBackfillTicketAsync(backfillTicketID);

this is full code

private const string NA = "n/a";
    public const int MAX_PLAYERS = 100;


    private static string _allocationID;
    private static bool _doBackFilling = false;
    private static IServerQueryHandler _serverQueryHandler;
    private static BackfillTicket _localBackfillTicket;
    private static string _backfillTicketID;

    private static bool AllowEnter
    {
        get
        {
            return NetworkManager.Instances.ElementAt(0).ServerManager.Clients.Count < MAX_PLAYERS;
        }
    }


    public static async void StartServer(string externalServerIP, ushort serverPort)
    {
        Debug.Log(nameof(StartServer));

        Debug.Log($"Init Server");
        Camera.main.enabled = false;
        QualitySettings.vSyncCount = 0;
        Application.targetFrameRate = 30;


        Debug.Log($"Start Server Connection");
        var networkManager = NetworkManager.Instances.ElementAt(0);
        networkManager.ServerManager.StartConnection(serverPort);
        networkManager.ServerManager.OnRemoteConnectionState += OnRemoteConnectionState;


        Debug.Log($"Start Server Services");
        var option = new InitializationOptions();
        option.SetEnvironmentName("production");
        await UnityServices.InitializeAsync(option);


        Debug.Log($"Start Server Query Handler");
        var multiplayService = MultiplayService.Instance;
        _serverQueryHandler = await multiplayService.StartServerQueryHandlerAsync(MAX_PLAYERS, "TestServer", NA, NA, NA);


        Debug.Log("Ready Server For Players");
        await multiplayService.ReadyServerForPlayersAsync();


        Debug.Log("Get MatchMaker Payload");
        var serverCallbacks = new MultiplayEventCallbacks();
        serverCallbacks.Allocate -= OnMultiplayerAllocation;
        serverCallbacks.Allocate += OnMultiplayerAllocation;
        var sereverEvents = await multiplayService.SubscribeToServerEventsAsync(serverCallbacks);


        var serverConfigs = multiplayService.ServerConfig;
        Debug.Log($"Server ID[{serverConfigs.ServerId}]");
        Debug.Log($"Server Allocation ID[{serverConfigs.AllocationId}]");
        Debug.Log($"Server Port[{serverConfigs.Port}]");
        Debug.Log($"Server Query Port[{serverConfigs.QueryPort}]");
        Debug.Log($"Server Log Directory[{serverConfigs.ServerLogDirectory}]");


        Debug.Log($"Wait for Allocation ID");
        while (string.IsNullOrEmpty(_allocationID))
        {
            var configID = multiplayService.ServerConfig.AllocationId;

            if (string.IsNullOrEmpty(configID) == false && string.IsNullOrEmpty(_allocationID))
            {
                Debug.Log($"Set Allocation ID With Config[{configID}]");
                _allocationID = configID;
            }

            await UniTask.DelayFrame(100);
        }


        Debug.Log($"Get Payload Allocation");
        var matchmakingResult = await MultiplayService.Instance.GetPayloadAllocationFromJsonAs<MatchmakingResults>();

        Debug.Log("Start Backfill Ticket");
        var backfillProperties = new BackfillTicketProperties(matchmakingResult.MatchProperties);

        Debug.Log($"ID: {matchmakingResult.MatchId}, QueueName: {matchmakingResult.QueueName}, Properties: {backfillProperties}");
        _localBackfillTicket = new BackfillTicket { Id = matchmakingResult.MatchId, Properties = backfillProperties };
        _backfillTicketID = _localBackfillTicket.Id;

        Debug.Log("Start Backfilling");
        _doBackFilling = true;
        await TryBackFilling(networkManager, _backfillTicketID);
        _doBackFilling = false;
    }

    public static void UpdateServer()
    {
        if (_serverQueryHandler == null) { return; }

        if (NetworkManager.Instances.ElementAt(0).IsServer == false) { return; }

        _serverQueryHandler.CurrentPlayers = (ushort)NetworkManager.Instances.ElementAt(0).ServerManager.Clients.Count;

        _serverQueryHandler.UpdateServerCheck();
    }

    private static async UniTask TryBackFilling(NetworkManager networkManager, string backfillTicketID)
    {
        Debug.Log(nameof(TryBackFilling));

        while (_doBackFilling && AllowEnter)
        {
            Debug.Log($"BackfillTicket ID: {backfillTicketID}");

            var matchmaker = MatchmakerService.Instance;
            Debug.Log($"Matchmaker: {matchmaker}");

            var localBackfillTicket = await MatchmakerService.Instance.ApproveBackfillTicketAsync(backfillTicketID);
            Debug.Log($"Local BackfillTicket ID: {localBackfillTicket.Id}");
            backfillTicketID = localBackfillTicket.Id;

            await UniTask.DelayFrame(2000);
        }
    }


    private static void OnRemoteConnectionState(NetworkConnection connection, RemoteConnectionStateArgs args)
    {
        Debug.Log(nameof(OnRemoteConnectionState));

        var networkManager = NetworkManager.Instances.ElementAt(0);

        switch (args.ConnectionState)
        {
            case RemoteConnectionState.Stopped:
                if (networkManager.ServerManager.Clients.Count == 0)
                {
                    Debug.Log("Server Stopp by all clients disconnecting");
                    Application.Quit();
                    break;
                }

                if (_doBackFilling == false && AllowEnter)
                {
                    TryBackFilling(networkManager, _backfillTicketID).Forget();
                }
                break;
        }
    }

    private static void OnMultiplayerAllocation(MultiplayAllocation allocation)
    {
        Debug.Log(nameof(OnMultiplayerAllocation));

        Debug.Log($"Allocation ID [{allocation.AllocationId}]");
        _allocationID = allocation.AllocationId;
    }

this is error message

I spend too many time about this problem…
if some body know answer plz help me

fix error by using

matchmakingResult.BackfillTicketId

@youngwoocho02 how did yu solve this???

just use matchmakingResult.BackfillTicketId after allocation