How can I use p:selectonemenu with a pojo from hibernate?

Question

I have to a select one menu, and this is not sending the code from the view to the object into the managed beans. I don't know what happened.

View:

<p:selectOneMenu value="#{administracionEmpresas.faxServer}" style="margin-bottom: -6px" converter="faxServerConverter" required="true">                                                               
    <f:selectItem itemLabel="FaxServer" itemValue="" noSelectionOption="true"/>
    <f:selectItems value="#{administracionEmpresas.listFaxServer}"  var="faxServer" itemLabel="#{faxServer.descripcion}" itemValue="#{faxServer}"/>  
</p:selectOneMenu>

Converter:

@Override
public Object getAsObject(FacesContext context, UIComponent component, String value) {
    if (value.trim().isEmpty()) {
        System.out.println("Valor:" +value);
        SlpFaxServer e = new SlpFaxServer();
        e.setIdFaxServer("173ace38-7");
        return e;
    } else {
        funciones = new FuncionesHibernate(SlpFaxServer.class);
        System.out.println("Id Fax Server: " + value);
        SlpFaxServer var = funciones.getEntidad(value.toString());
        System.out.println("Valor ID:" + var.getIdFaxServer());
        return var;
    }
}

@Override
public String getAsString(FacesContext context, UIComponent component, Object value) {        
    if (value != null && value instanceof SlpFaxServer) {
        SlpFaxServer var = (SlpFaxServer) value;
        System.out.println("Valor getAsString: " + var.getIdFaxServer());
        return "" + var.getIdFaxServer();
    }
    return "";

}