BuddyPress.org

I’m trying to create a block with notifications that should be displayed using a shortcode, but for some reason I get one message (Error: Unable to retrieve notification data.) in the place of the notifications themselves. Tell me where did I mess up?
The code itself:

<?php
/*
Plugin Name: BuddyPress Real-Time Notifications
Description: 
Version: 1.0
Author: 
*/

// JavaScript
function bprtn_enqueue_scripts() {
    wp_enqueue_script('bprtn-scripts', plugin_dir_url(__FILE__) . 'scripts.js', array('jquery'), null, true);
}

add_action('wp_enqueue_scripts', 'bprtn_enqueue_scripts');

// CSS
function bprtn_enqueue_styles() {
    wp_enqueue_style('bprtn-styles', plugin_dir_url(__FILE__) . 'styles.css');
}

add_action('wp_enqueue_scripts', 'bprtn_enqueue_styles');

// function
function bprtn_display_notification($notification) {
    if (isset($notification->component_name) && isset($notification->component_action) && isset($notification->item_id)) {
        echo '<div class="bprtn-notification">';
        echo '<p class="bprtn-description">' . bp_the_notification_description($notification->component_action, $notification->item_id) . '</p>';
        echo '<p class="bprtn-date">' . bp_the_notification_time_since($notification->date_notified) . '</p>';
        echo '<div class="bprtn-actions">';
        // buttons
        bp_the_notification_action_links(array('before' => '<div class="bprtn-action">', 'after' => '</div>', 'notification' => $notification));
        echo '</div>';
        echo '</div>';
    } else {
        echo '<p class="bprtn-notification-error">Error: Unable to retrieve notification data.</p>';
    }
}

// function load notifications
function bprtn_load_notifications() {
    $user_id = bp_loggedin_user_id();
    $notifications = bp_notifications_get_notifications_for_user($user_id);

    if (!empty($notifications)) {
        foreach ($notifications as $notification) {
            bprtn_display_notification($notification);
        }
    } else {
        echo '<p class="bprtn-no-notifications">No new notifications.</p>';
    }
}

// shortcode
function bprtn_notifications_shortcode() {
    ob_start();
    bprtn_load_notifications();
    return ob_get_clean();
}

add_shortcode('bprtn_notifications', 'bprtn_notifications_shortcode');

// AJAX
function bprtn_mark_as_read() {
    if (isset($_POST['notification_id'])) {
        $notification_id = $_POST['notification_id'];
        bp_notifications_mark_notifications_by_id(array($notification_id), 'read');
    }
    wp_die();
}

add_action('wp_ajax_bprtn_mark_as_read', 'bprtn_mark_as_read');
?>