[Unity5.7]Never spawn playerPref without error

I’m constructing multi-player board_game_like game, in which I use NetworlLobbyManager inherited class and LobbyPlayer inherited class(LobbyPlayer). I change ready_state and scene like below.

    public void Ready()
        {
            lobbyPlayer.CmdGetReady();
            lobbyPlayer.SendReadyToBeginMessage();
        }

it is bonded to Bottun.CmdGetReady() is only about the signs to tell being ready.

 public override void OnLobbyServerPlayersReady()
    {
        ready = true;
    }

 private void LobbyBehaviour()
    {
        if (ready)
        {
            if (CDforPlay > 0)
            {
                CDforPlay -= Time.deltaTime;
            }
            else
            {
                if (GameSceneFlg == false)
                {
                    ServerChangeScene(playScene);
                    Debug.Log("GamScene");
                    GameSceneFlg = true;
                }
            }
        }

LobbyBehaviour() exists in Update().

In editor and build, playScene is successfully loaded. However, playerPrefab never spawns. Without player objects, I can never set player information to this scene.
Particularly, this symptom occurs without error (at least OnServerAddPlayer Called).I confiemed OnServerAddPlayer() is called when the game changed to playScene.

I tried some tests in another project using similar code. Then playerPrefab spawned. So, codes above may not the mistaking part. If you have any piece of knowledge, please tell me. Thank you in advance.

[Probrem Cleared]

The cause was OnlineLobbyManager inherited class. We cannot inherit OnlineLobbyManager probably.