While ClickSeries is fired with Area and Bar, it's not being fired with Line, FastLine and Points series. Therefore, ClickPointer event isn't fired either.

A workaround is using the Touch event, for example:

    void tChart1_Touch(object sender, View.TouchEventArgs e)
    {
      for (int i = 0; i < tChart1.Series.Count; i++)
      {
        if (tChart1[i] is Steema.TeeChart.Styles.CustomPoint)
        {
          int x = Steema.TeeChart.Utils.Round(e.Event.GetX());
          int y = Steema.TeeChart.Utils.Round(e.Event.GetY());

          Steema.TeeChart.Styles.CustomPoint p = (Steema.TeeChart.Styles.CustomPoint)tChart1[i];
          int index = p.Clicked(x, y);

          if (index != -1)
          {
            this.Points_ClickPointer(p, index, x, y);
            break;
          }
        }
      }
    }

    void Points_ClickPointer(CustomPoint series, int valueIndex, int x, int y)
    {
      new AlertDialog.Builder(this)
      .SetTitle("Alert1")
      .SetMessage("ValueIndex is: " + valueIndex.ToString())
      .SetPositiveButton("OK", null as IDialogInterfaceOnClickListener)
      .Show();
    }