im getting a plugin error for the "new order notification for woocommerce" plugin

my site is working fine, however when I click on this error its displaying the following error under debugging:

Fatal error: Uncaught Error: Call to a member function get_items() on bool in /var/www/vhosts/delivered2u.co/httpdocs/wp-content/plugins/new-order-notification-for-woocommerce/new-order-notification-admin.php:114 Stack trace: #0 /var/www/vhosts/delivered2u.co/httpdocs/wp-includes/class-wp-hook.php(292): new_order_notification_menu() #1 /var/www/vhosts/delivered2u.co/httpdocs/wp-includes/class-wp-hook.php(316): WP_Hook->apply_filters() #2 /var/www/vhosts/delivered2u.co/httpdocs/wp-includes/plugin.php(484): WP_Hook->do_action() #3 /var/www/vhosts/delivered2u.co/httpdocs/wp-admin/admin.php(259): do_action() #4 {main} thrown in /var/www/vhosts/delivered2u.co/httpdocs/wp-content/plugins/new-order-notification-for-woocommerce/new-order-notification-admin.php on line 114

no plugins have been edited. I believe the site might have updated to the lates version of Wordpress, but that's about it..

any help is appreciated