Rad Combobox Loader or please wait not showing when selected index changed - Telerik Rad combobox

 <telerik:RadComboBox ID="ddlRCNo" runat="server" AutoPostBack="true" OnSelectedIndexChanged="ddlRCNo_SelectedIndexChanged"  InitialValue="0" CssClass="uk-width-1-2" Filter="Contains" CheckBoxes="false" EnableCheckAllItemsCheckBox="false" Style="width: 50% !important;">

                                                            <Localization CheckAllString="Select All" />

                                                        </telerik:RadComboBox>

remove property ClientIDMode="Static"