I copied the example code verbatim from the documentation. There does not appear to be any card-related css being applied. For example there are no background colors, padding or dividing lines. However, the responsive menu and grid appear to be working correctly so it seems the page is loading the intended Foundation css and js.
Here's the page rendering the Card code:
Is there something missing in the build for 6.3 for Cards or is there something wrong with the example code copied below from the 6.3 documentation:
<div class="card" style="width: 300px;">
This is a header
<h4>This is a card.</h4>
<p>It has an easy to override visual style, and is appropriately subdued.</p>