Image Carousel Error Message at bottom of page

This error appears at the bottom of my web page when I am logged in.

Fatal error: Call to undefined function is_plugin_active() in /home2/ovcpath0/public_html/phrn.net/wp-content/plugins/image-carousel/inc/functions/icp-functions.php on line 102

It is causing issues with logging into the site and staying logged in. At this point I don’t see any other obvious issues.

The website is www.phrn.net

Thanks for your help.
Nathalie