Tracker not working in pie series

Hello there,

I have implemented a Pie Series with several pie slices and it's showing fine, but the tracker is not working.

This is on WPF. 

Tracker is working fine with other kind of series, but not on this one.

No error is showing on the console so I don't know what exactly to report.

This is my code:

PlotModel modelo = new PlotModel();
PieSeries serie = new PieSeries();
serie.InnerDiameter = 0.4;
serie.Diameter = 0.8;
modelo.Series.Add(serie);


int indice = 0;
foreach (MotivoDevolucion motivo in Datos.motivos.Values)
{
}