在 WordPress 中，wp_ajax_nopriv_(action) 为未登录的用户执行.如果您希望它在前端为访问者和登录用户触发，您可以这样做:

In WordPress, wp_ajax_nopriv_(action) executes for users that are not logged in. if you want it to fire on the front-end for both visitors and logged-in users, you can do this:

add_action( 'wp_ajax_my_action', 'my_action' );
add_action( 'wp_ajax_nopriv_my_action', 'my_action' );

所以在你的例子中像这样添加

So in your example add like this

add_action( 'wp_ajax_my_get_process_payment', 'get_process_payment' );
add_action( 'wp_ajax_nopriv_get_process_payment', 'get_process_payment' );
function get_process_payment(){
   echo "test";
   wp_die();
}

请查看https://codex.wordpress.org/AJAX_in_Plugins了解更多详情