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
[quote]
StartServer
Init Server
Start Server Connection
Start Server Services
Start Server Query Handler
SQP server: SQP server started on 0.0.0.0:9010
Ready Server For Players
Get MatchMaker Payload
[Wire]: Attempting connection on: ws://127.0.0.1:8086/v1/connection/websocket
OnRemoteConnectionState
[Wire]: Websocket connected to : ws://127.0.0.1:8086/v1/connection/websocket. Initiating Wire handshake.
Server ID[66595334]
Server Allocation ID[d4630423-639e-4bd1-8ada-749104ce0c45]
Server Port[9000]
Server Query Port[9010]
Server Log Directory[/mnt/unity/logs/]
Wait for Allocation ID
Set Allocation ID With Config[d4630423-639e-4bd1-8ada-749104ce0c45]
OnMultiplayerAllocation
Allocation ID [d4630423-639e-4bd1-8ada-749104ce0c45]
Get Payload Allocation
Start Backfill Ticket
ID: 7ddee6a3-ccd6-4aae-9299-ce0605bb9985, QueueName: NetowrkTestQueue01, Properties: Unity.Services.Matchmaker.Models.BackfillTicketProperties
Start Backfilling
TryBackFilling
BackfillTicket ID: 7ddee6a3-ccd6-4aae-9299-ce0605bb9985
Matchmaker: Unity.Services.Matchmaker.WrappedMatchmakerService

Title: Not Found
Errors:
{"Ticket":["Backfill Ticket 7ddee6a3-ccd6-4aae-9299-ce0605bb9985 not found"]}
HttpException1: (404) HTTP/1.1 404 Not Found
at Unity.Services.Matchmaker.Http.ResponseHandler.HandleAsyncResponse (Unity.Services.Matchmaker.Http.HttpClientResponse response, System.Collections.Generic.Dictionary
2[TKey,TValue] statusCodeToTypeMap) [0x0006d] in .\Library\PackageCache\com.unity.services.matchmaker@1.1.1\Runtime\Http\ResponseHandler.cs:122
at Unity.Services.Matchmaker.Http.ResponseHandler.HandleAsyncResponseT [0x00000] in .\Library\PackageCache\com.unity.services.matchmaker@1.1.1\Runtime\Http\ResponseHandler.cs:226
at Unity.Services.Matchmaker.Apis.Backfill.BackfillApiClient.ApproveBackfillTicketAsync (Unity.Services.Matchmaker.Backfill.ApproveBackfillTicketRequest request, System.String payloadProxyToken, Unity.Services.Matchmaker.Configuration operationConfiguration) [0x0011f] in .\Library\PackageCache\com.unity.services.matchmaker@1.1.1\Runtime\Apis\BackfillApi.cs:131
at Unity.Services.Matchmaker.WrappedMatchmakerService.TryCatchRequestTRequest,TReturn [0x00045] in .\Library\PackageCache\com.unity.services.matchmaker@1.1.1\Runtime\SDK\WrappedMatchmakerService.cs:320
Rethrow as MatchmakerServiceException: HTTP/1.1 404 Not Found
at Unity.Services.Matchmaker.WrappedMatchmakerService.ResolveErrorWrapping (Unity.Services.Matchmaker.MatchmakerExceptionReason reason, System.Exception exception) [0x00105] in .\Library\PackageCache\com.unity.services.matchmaker@1.1.1\Runtime\SDK\WrappedMatchmakerService.cs:380
at Unity.Services.Matchmaker.WrappedMatchmakerService.TryCatchRequestTRequest,TReturn [0x0010f] in .\Library\PackageCache\com.unity.services.matchmaker@1.1.1\Runtime\SDK\WrappedMatchmakerService.cs:343
at Unity.Services.Matchmaker.WrappedMatchmakerService.ApproveBackfillTicketAsync (System.String backfillTicketId) [0x000bb] in .\Library\PackageCache\com.unity.services.matchmaker@1.1.1\Runtime\SDK\WrappedMatchmakerService.cs:155
at SimpleServer.TryBackFilling (FishNet.Managing.NetworkManager networkManager, System.String backfillTicketID) [0x00064] in C:\Unity Workspace\NetworkTest\Assets\Scripts\SimpleServer.cs:304
at Cysharp.Threading.Tasks.CompilerServices.AsyncUniTask`1[TStateMachine].GetResult (System.Int16 token) [0x00000] in .\Library\PackageCache\com.cysharp.unitask@cfe509a556\Runtime\CompilerServices\StateMachineRunner.cs:218
at SimpleServer.StartServer (System.String externalServerIP, System.UInt16 serverPort) [0x00510] in C:\Unity Workspace\NetworkTest\Assets\Scripts\SimpleServer.cs:278
at System.Runtime.CompilerServices.AsyncMethodBuilderCore+<>c.b__7_0 (System.Object state) [0x00000] in <085207daa9364a21b9bc438dc250c23d>:0
at UnityEngine.UnitySynchronizationContext+WorkRequest.Invoke () [0x00002] in /home/bokken/build/output/unity/unity/Runtime/Export/Scripting/UnitySynchronizationContext.cs:153
at UnityEngine.UnitySynchronizationContext.Exec () [0x0005d] in /home/bokken/build/output/unity/unity/Runtime/Export/Scripting/UnitySynchronizationContext.cs:83
at UnityEngine.UnitySynchronizationContext.ExecuteTasks () [0x00014] in /home/bokken/build/output/unity/unity/Runtime/Export/Scripting/UnitySynchronizationContext.cs:107
[/quote]

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