Description Source not working

For some reason the plugin is not pulling the post title for the description of the pin. All I get is “Tell us about this Pin…” even though the Description Source for Post Title is checked. Images within the post are being uploaded through an ACF (Advanced Custom Field) Field. Would that make a difference?

Here is an example post: https://sugarandcharm.com/2017/03/best-chocolate-chip-cookie-recipe.html

Thanks in advance for any help you can provide.
P