Can't select an item in the scrollPane in LibGDX

guys. I was looking at an article that drew a list of selectable sequences in a scrollable layout for the game LibGDX. I did everything according to the lesson, but the mena doesn't have a choice of items.

public ChangeSongState(GameStateManager game) {
    super(game);
    atlas = new TextureAtlas(Gdx.files.internal("uiskin.atlas"));
    skin = new Skin(Gdx.files.internal("SimpleSkin.json"), atlas);
}

@Override
public void update(float dt) {
    Gdx.gl.glClearColor(0, 0, 0, 1); 
    Gdx.gl.glBlendFunc(GL20.GL_SRC_ALPHA, GL20.GL_ONE_MINUS_SRC_ALPHA);
    Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);

    stage.act(dt);
    stage.draw();
}

@Override
public void render(SpriteBatch sb) {
    gameWidth = Gdx.graphics.getWidth();
    gameHeight = Gdx.graphics.getHeight();
    list = new List<String>(skin);
    String[] strings = new String[20];
    for (int i = 0, k = 0; i < 20; i++) {
        strings[k++] = "String: " + i;

    }
    list.setItems(strings);

    scrollPane = new ScrollPane(list);
    scrollPane.setBounds(0, 0, gameWidth, gameHeight + 100);
    scrollPane.setSmoothScrolling(false);
    scrollPane.setPosition(gameWidth / 2 - scrollPane.getWidth() / 4,
            gameHeight / 2 - scrollPane.getHeight() / 4);
    scrollPane.setTransform(true);
    scrollPane.setScale(0.5f);
    stage = new Stage(new StretchViewport(gameWidth, gameHeight));
    stage.addActor(scrollPane);
    Gdx.input.setInputProcessor(stage);
}

Json-file:

"com.badlogic.gdx.scenes.scene2d.ui.List$ListStyle": {
    "default": {
      "font": "default-font",
      "fontColorUnselected":"blue",
      "fontColorSelected":"white",
      "selection": "selection"
    }
  }

Can't understand why I can't select a list item