error in variation

in variable product the groups not show
and this problem show

Warning: call_user_func_array() expects parameter 1 to be a valid callback, array must have exactly two members in /home/woodzoco/public_html/printat.net/wp-includes/plugin.php on line 496

https://ww.wp.xz.cn/plugins/woocommerce-product-price-based-on-countries/