Webflow seemed to start prefixing with the w-
the classes for tab links and tab panes , causing the selectors for the original script to break. Just update your snippets so it matches the following:
<!-- START FIX: Always show the first tab first -->
<script>
$(".tab-link").removeClass("w--current");
$(".tab-pane").removeClass("w--tab-active");
$(".tab-link:nth-child(1)").addClass("w--current");
$(".tab-pane:nth-child(1)").addClass("w--tab-active");
</script>
<!-- END FIX: Always show the first tab first -->