I'm trying to make it so when the user selects a certain item it gives the user some information by setting the visible property of a label to "true", it should be relatively simple but i can't seem to make it work. I'm using Web Forms.

Aspx code:

<label for="footerPlaceHolder_twoFactorAuthentication" class="sr-only"><asp:Localize runat="server" Text="<%$ Resources:UserMessages, SelectTwoFactor %>"></asp:Localize></label> <asp:DropDownList runat="server" ID="twoFactorAuthenticationDropDownList" OnSelectedIndexChange="twoFactorAuthenticationDropDownList_SelectedIndex" CssClass="selectpicker"> <asp:ListItem Value="0" Text = "<%$ Resources:UserMessages, SelectTwoFactor %>"></asp:ListItem> <asp:ListItem Value="1" Text = "<%$ Resources:UserMessages, RequireTwoFactor %>" ></asp:ListItem> <asp:ListItem Value="2" Text = "<%$ Resources:UserMessages, RecommendTwoFactor %>" ></asp:ListItem> <asp:ListItem Value="3" Text = "<%$ Resources:UserMessages, TwoFactorNotRequired %>" ></asp:ListItem> </asp:DropDownList> <p><asp:RequiredFieldValidator runat="server" ControlToValidate="paymentDay" CssClass="field-validation-error" ErrorMessage="<%$ Resources:ErrorMessages, ValidationPaymentDayRequired %>" InitialValue="0" EnableClientScript="true" Display="Dynamic"></asp:RequiredFieldValidator></p> <h3><asp:Localize runat="server" ID="noticeLabel" Visible="false" Text="<%$ Resources:UserMessages, Notice %>"></asp:Localize></h3> <h5 class="leftspace"><asp:Localize runat="server" ID="noticeText" Visible="false" Text="<%$ Resources:UserMessages, NoticeInfo %>"></asp:Localize></h5>

What I've tried: