The number one reason for this is copy/pasting from a web page into the WordPress Visual post editor. Any HTML that was copied will also be pasted. This HTML will break the WordPress shortcode parser. With that said, give this a go…
Edit the page where you have inserted the
[connections enable_category_select='FALSE'] shortcode.
Text tab in the post editor.
Delete any HTML in and around the shortcode.
If that was the reason, that will fix it up. Let me know, thanks.
Hope that helps!