I need some help to add reCAPTCHA function to my advanced search page. zc 1.57c. Google reCAPTCHA v3.4

I tried to add <?php echo recaptcha_get_html(); ?> to tpl_advanced_search_default.php. The reCAPTCHA button shows up in my advanced search page, but it does not work.

In includes/includes/classes/observers/class.google_recaptcha.php, I changed the following code:

Under function __construct(), following code is added:

$pages_to_check[] = 'NOTIFY_ADVANCED_SEARCH_CAPTCHA_CHECK';

Under $event_array, NOTIFY_ADVANCED_SEARCH_CAPTCHA_CHECK' => 'advanced_search' is added. I tried to use "advanced_search", "advanced_search_result" even "contact", no help.

In includes/modules/pages/advanced_search_result/header_php.php I added the following code at the last line. No help.

$zco_notifier->notify('NOTIFY_ADVANCED_SEARCH_CAPTCHA_CHECK', $_POST);

In includes/modules/pages/advanced_search/header_php.php advanced_search I added the following code at the first line. No help.

$zco_notifier->notify('NOTIFY_ADVANCED_SEARCH_CAPTCHA_CHECK', $_POST);