Plugin no longer works with {/slug-pattern}

It worked when I first installed it, I loved it, users loved it, life was good. A year or so into using it, we can’t access the custom slug we created. We accessed the site via “mysite.com{/slug-pattern}”, but that no longer works. It seems I now have to use “mysite.com{?slug-pattern}”, which is a change I didn’t expect or want. How can we change this back?