Not all series contained in the Series collection may be displayed. If the ChartView.ViewType is ChartType.Pie, only one series is shown, although the series collection may contain several series.
Note the difference between series collections obtained using the Series and the ChartObject.Series properties. The ChartObject.Series collection may contain series not included in any view. For example, this may happen in a column chart with two series if one of the series changes its type to ChartType.Pie and a new series is added to the chart.
Therefore, when adding a new series, add it to a view of a particular ChartView.ViewType to make sure that it is displayed using that type.