Why does my Bootstrap popover not work?

You forgot this : https://getbootstrap.com/docs/3.4/javascript/#callout-popover-opt-in

For performance reasons, the Tooltip and Popover data-apis are opt-in, meaning you must initialize them yourself.

One way to initialize all tooltips on a page would be to select them by their data-toggle attribute:

$(function () {
    $('[data-toggle="popover"]').popover()
})

<a tabindex="0" class="btn btn-lg btn-danger" role="button" data-toggle="popover" data-trigger="focus" title="Dismissible popover" data-content="And here's some amazing content. It's very engaging. Right?" id="example">Dismissible popover</a>

This method is required

$('#example').popover('show');

DEMO