Fatal error

Any ideas why I am getting the following error please?

Fatal error: Uncaught Error: Call to a member function get_cart_contents_count() on null in /homepages/36/d696176350/htdocs/app696176515/wp-content/plugins/woo-cart-count-shortcode/woocommerce-cart-count-shortcode.php:40 Stack trace: #0 /homepages/36/d696176350/htdocs/app696176515/wp-includes/shortcodes.php(319): woocommerce_cart_count_shortcode(Array, ”, ‘cart_button’) #1 [internal function]: do_shortcode_tag(Array) #2 /homepages/36/d696176350/htdocs/app696176515/wp-includes/shortcodes.php(197): preg_replace_callback(‘/\\[(\\[?)(do_wid…’, ‘do_shortcode_ta…’, ‘[cart_button ic…’) #3 /homepages/36/d696176350/htdocs/app696176515/wp-includes/class-wp-hook.php(286): do_shortcode(‘[cart_button ic…’) #4 /homepages/36/d696176350/htdocs/app696176515/wp-includes/plugin.php(203): WP_Hook->apply_filters(‘[cart_button ic…’, Array) #5 /homepages/36/d696176350/htdocs/app696176515/wp-content/plugins/wordpress-seo/admin/links/class-link-watcher.php(116): apply_filters(‘the_content’, ‘[cart_button ic…’) #6 /homepages/36/d69617 in /homepages/36/d696176350/htdocs/app696176515/wp-content/plugins/woo-cart-count-shortcode/woocommerce-cart-count-shortcode.php on line 40