Cannot view other user posts

We have a private site where users must log into WordPress.
There are several pages with categorical lists for users to post and comment on using a shortcode in the following format:
[frontier-post frontier_list_cat_id="42"]

Users can post and comment okay but only on their own posts and comments. Nobody can see any other user’s posts or comments. This includes the site admin account which has all user capabilities.

How do I fix it so all users can see and comment on all other user posts?

Thanks.

https://www.ads-software.com/plugins/frontier-post/