Fatal error: Uncaught Error: Call to undefined function is_checkout() in /mnt/web504/c1/93/511302593/htdocs/STRATO-apps/wordpress_01/app/wp-content/plugins/woo-checkout-field-editor-pro/public/class-thwcfd-public-checkout.php:22 Stack trace: #0 /mnt/web504/c1/93/511302593/htdocs/STRATO-apps/wordpress_01/app/wp-includes/class-wp-hook.php(307): THWCFD_Public_Checkout->enqueue_styles_and_scripts() #1 /mnt/web504/c1/93/511302593/htdocs/STRATO-apps/wordpress_01/app/wp-includes/class-wp-hook.php(331): WP_Hook->apply_filters() #2 /mnt/web504/c1/93/511302593/htdocs/STRATO-apps/wordpress_01/app/wp-includes/plugin.php(476): WP_Hook->do_action() #3 /mnt/web504/c1/93/511302593/htdocs/STRATO-apps/wordpress_01/app/wp-includes/script-loader.php(2156): do_action() #4 /mnt/web504/c1/93/511302593/htdocs/STRATO-apps/wordpress_01/app/wp-includes/class-wp-hook.php(307): wp_enqueue_scripts() #5 /mnt/web504/c1/93/511302593/htdocs/STRATO-apps/wordpress_01/app/wp-includes/class-wp-hook.php(331): WP_Hook->apply_filters() #6 /mnt/web504/c1/93/51130 in /mnt/web504/c1/93/511302593/htdocs/STRATO-apps/wordpress_01/app/wp-content/plugins/woo-checkout-field-editor-pro/public/class-thwcfd-public-checkout.php on line 22