Sterling database is not saved on Windows phone

I have followed database examples from multiple instances. None of them work for me. When I save some things in my database, everything is clearly saved using sterling (on my phone, not an emulator) when debugging. However, when I restart my application, the database is empty. Someone else is experiencing the same problem. Or does someone have a complete working example. I know my serialization and rescue works ... Until I reload the app, load my works ...

The code is in my application.

    public static ISterlingDatabaseInstance Database { get; private set; }
    private static SterlingEngine _engine;
    private static SterlingDefaultLogger _logger;

    private void Application_Launching(object sender, LaunchingEventArgs e)
    {
        ActivateEngine();
    }

    // Code to execute when the application is activated (brought to foreground)
    // This code will not execute when the application is first launched
    private void Application_Activated(object sender, ActivatedEventArgs e)
    {
        ActivateEngine();
    }

    // Code to execute when the application is deactivated (sent to background)
    // This code will not execute when the application is closing
    private void Application_Deactivated(object sender, DeactivatedEventArgs e)
    {
        DeactivateEngine();
    }

    // Code to execute when the application is closing (eg, user hit Back)
    // This code will not execute when the application is deactivated
    private void Application_Closing(object sender, ClosingEventArgs e)
    {
        DeactivateEngine();
    }



    private void ActivateEngine()
    {
        _engine = new SterlingEngine();
        _logger = new SterlingDefaultLogger(SterlingLogLevel.Information);
        _engine.Activate();
        Database = _engine.SterlingDatabase.RegisterDatabase<SokobanDb>();
    }

    private void DeactivateEngine()
    {
        _logger.Detach();
        _engine.Dispose();
        Database = null;
        _engine = null;
    }

      

        
        
        
      

    

Code in my ModelModel

    public void LoadState(int level)
    {
        var levelState = App.Database.Load<LevelState>(level);
        if (levelState != null)
        {
            //TODO: check if game started, then create board from boardstring property else create new board
            //Labyrint = new Labyrint(Factory.CreateBoard());
            NewGame(level);
        }
        else
        {
            NewGame(level);
        }
    }

    public void SaveState()
    {
        var levelState = new LevelState { LevelId = _level, Moves = Labyrint.Moves, Board = Labyrint.ToString() };
        App.Database.Save(levelState);
        App.Database.Flush(); //Required to clean indexes etc.
    }