Fatal error: Uncaught Error: Call to undefined function WP_STATISTICS\add_action() in /usr/local/www/irenakulesza.pl/wp-content/plugins/wp-statistics/includes/admin/class-wp-statistics-admin-ajax.php:21 Stack trace: #0 /usr/local/www/irenakulesza.pl/wp-content/plugins/wp-statistics/includes/admin/class-wp-statistics-admin-ajax.php(305): WP_STATISTICS\Ajax->__construct() #1 {main} thrown in /usr/local/www/irenakulesza.pl/wp-content/plugins/wp-statistics/includes/admin/class-wp-statistics-admin-ajax.php on line 21