Stopped working in WP 5.8.3

I tried this in a page on my site a week ago when WordPress was still 5.8.2 and it worked great on posts and on pages. But today, I updated WP to 5.8.3 and the includeme shortcode no longer works.

I tried it on a page tonight and what I get is “Only admnistrator owned posts can execute the [includeme] shortcode. This message is shown only to administrators.”

I am the administrator so it should at least work for me. But it really needs to work for all administrators, site managers, authors, editors, and contributors who write/edit posts and pages.

I was really hoping this would work so I can replace all my PHP includes statements with includeme shortcodes. Can you update it to work for everyone in WP 5.8.3? Please and thank you.