Recent Comments in Sidebar

I’m trying to move the Recent Comments from the bottom of the page to the sidebar on https://obsessionfitness.com

When I add the code with or without arguments I get this error.
Fatal error: Call to undefined function: src_simple_recent_comments() in /home/content/o/f/s/ofsschone/html/wp-content/themes/abstractia-10/sidebar.php on line 32

Here’s the plugin page:
https://www.g-loaded.eu/2006/01/15/simple-recent-comments-wordpress-plugin/

Thanks for any help.