Cannot show a DxPopup

I used the following to create a new app

dotnet new dx.blazor -n MyBlazorServerApp --interactivity Server

I then added DxPopup components to the main page, but they do not appear.

Razor
@page "/"
<PageTitle>Welcome</PageTitle>

<div class="main-content">
    <DxPopup @bind-Visible=Popup1Visible ShowCloseButton=@false ShowFooter CloseOnOutsideClick=@false CloseOnEscape=@false ShowHeader>
        <HeaderContentTemplate>
            Popup 1
        </HeaderContentTemplate>
        <BodyContentTemplate>
            First popup
        </BodyContentTemplate>
        <FooterContentTemplate>
            <DxButton CssClass="popup-button my-1 ms-2" RenderStyle="ButtonRenderStyle.Primary" Text="Open" Click=@(() => Popup2Visible = true) />
        </FooterContentTemplate>
    </DxPopup>

    <DxPopup @bind-Visible=Popup2Visible ShowCloseButton=@false ShowFooter CloseOnOutsideClick=@false CloseOnEscape=@false ShowHeader>
        <HeaderContentTemplate>
            Popup 2
        </HeaderContentTemplate>
        <BodyContentTemplate>
            Second popup
        </BodyContentTemplate>
        <FooterContentTemplate>
            <DxButton CssClass="popup-button my-1 ms-2" RenderStyle="ButtonRenderStyle.Primary" Text="Open" Click=@(() => Popup3Visible = true) />
            <DxButton CssClass="popup-button my-1 ms-2" RenderStyle="ButtonRenderStyle.Secondary" Text="Close" Click=@(() => Popup2Visible = false) />
        </FooterContentTemplate>
    </DxPopup>


    <DxPopup @bind-Visible=Popup3Visible ShowCloseButton=@false ShowFooter CloseOnOutsideClick=@false CloseOnEscape=@false ShowHeader>
        <HeaderContentTemplate>
            Popup 3
        </HeaderContentTemplate>
        <BodyContentTemplate>
            Third popup
        </BodyContentTemplate>
        <FooterContentTemplate>
            <DxButton CssClass="popup-button my-1 ms-2" RenderStyle="ButtonRenderStyle.Secondary" Text="Close" Click=@(() => Popup3Visible = false) />
        </FooterContentTemplate>
    </DxPopup>

</div>

@code {
    bool Popup1Visible = true;
    bool Popup2Visible;
    bool Popup3Visible;
}