Radio Button event CheckedChanged does not fires

Hi,
I have a simple form with 2 radio button grouped. I´m trying to hide/show a DropDown Listbox with the event CheckedChanged, but this event never fires...
What I´m doing wrong?
 
Thanks!
 
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THIS IS THE CODE:
<asp:RadioButton ID="AgruparPorCategoriaRadio" runat="server" GroupName="CategoriaFechaRadio" Text="Categoría"/>
<br />
<asp:RadioButton ID="AgruparPorFechaRadio" runat="server" GroupName="CategoriaFechaRadio" Text="Fecha" />
 
AND THE CODE BEHIND:
Protected Sub AgruparPorCategoriaRadio_CheckedChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles AgruparPorCategoriaRadio.CheckedChanged
       AnticipacionList.SelectedIndex = 0
       AnticipacionList.Visible ...