With help from a friend was able to find a solution based on the change noted in this post: https://www.advancedcustomfields.com/blog/acf-pro-5-5-13-update/
However, despite what the post says, it seems that it actually isn’t set to false by default. I was able to get custom fields to return by adding:
add_filter('acf/settings/remove_wp_meta_box', '__return_false');
to my functions.php file within the theme.
