我几乎完全重新访问了您的代码，并设法修复了您的问题。
对于用户购买的产品的添加到购物车按钮，它现在被链接到Google网络研讨会的类似自定义按钮“加入网络研讨会”所取代。
重新访问的代码 （更新）：

// Admin Product - Add Google Meet link field
add_action('woocommerce_product_options_general_product_data', 'add_google_meet_link_custom_field');
function add_google_meet_link_custom_field() {
    echo '<div class="options_group">';

    woocommerce_wp_text_input( array(
        'id'            => 'google_meet_link',
        'label'         => __('Google Meet Link', 'text-domain'),
        'placeholder'   => 'Enter Google Meet Link',
        'desc_tip'      => 'true',
        'description'   => __('Add your Google Meet link.', 'text-domain')
    ) );

    echo '</div>';
}

// Admin Product - Save Google Meet link field data
add_action('woocommerce_admin_process_product_object', 'save_google_meet_link_custom_field');
function save_google_meet_link_custom_field( $product ) {
    if ( isset($_POST['google_meet_link']) ) {
        $product->update_meta_data( 'google_meet_link', sanitize_url($_POST['google_meet_link']) );
    } 
}

// Display Google Meet link on order details and thank you page (clickable)
add_action('woocommerce_order_details_after_order_table', 'display_google_meet_link_custom_field_value', 10, 1);
function display_google_meet_link_custom_field_value( $order ) {
    $has_link = false;
    $html     = '';

    foreach ( $order->get_items() as $item ) {
        $product = $item->get_product();
        $google_meet_link = $product->get_meta('google_meet_link');

        if ( $google_meet_link ) {
            $html .= '<p><a href="' . esc_url($google_meet_link) . '">' . esc_html($google_meet_link) . '</a></p>';
            $has_link = true;
        }
    }
    
    if ( $has_link ) {
        echo '<h3>' . __('Google Meet Link:', 'text-domain') . '</h3>';
        echo $html;
    }
}

// Function that check if the webinar link exist or return webinar link
function get_webinar_link( $product, $conditional = false ) {
    $link = $product->get_meta('google_meet_link');

    if ( $conditional ) {
        return ! $link ? false : true;
    } else {
        return $link;
    }
}

// The custom replacement button function
function join_webinar_button( $product = null ){
    if ( ! $product ) global $product;

    // HERE your custom button text and link
    $button_text = __('Join Webinar', 'woocommerce');
    $button_link = get_webinar_link( $product );
    
    // Display button
    echo '<a class="button webinar-on" href="'.$button_link.'">' . $button_text . '</a>';
}

// Function that check if the current product has been purchased by the customer
function has_purchased_product( $product_id = null, $user_id = null ) {
    global $wpdb;

    $product_id = ! $product_id ? get_the_ID() : $product_id;
    $user_id = ! $user_id ? get_current_user_id() : $user_id;

    // Returns an array of product Ids reviewed by the customer
    return $wpdb->get_var( "
        SELECT  COUNT( opl.order_item_id )
        FROM {$wpdb->prefix}wc_order_product_lookup as opl
        INNER JOIN {$wpdb->prefix}postmeta as pm ON pm.post_id = opl.order_id 
        WHERE pm.meta_key = '_customer_user' AND pm.meta_value = '{$user_id}' 
            AND opl.product_id = '{$product_id}'
    " );
}

// Replacing single product button add to cart by a custom button
add_action( 'woocommerce_single_product_summary', 'replace_single_add_to_cart_button', 1 );
function replace_single_add_to_cart_button() {
    global $product;

    // Targeting our product type and checking that the product is purchased by user
    if ( $product->is_type( 'simple' ) && get_webinar_link( $product, true ) && // 'google_meet_webinar'
        has_purchased_product( $product->get_id() ) ) 
    {
        remove_action( 'woocommerce_single_product_summary', 'woocommerce_template_single_add_to_cart', 30 );
         add_action( 'woocommerce_single_product_summary', 'join_webinar_button', 30 );
    }
}

// Shop and archives pages: Replacing add to cart button by a link to the product
add_filter( 'woocommerce_loop_add_to_cart_link', 'replace_loop_add_to_cart_button', 10, 2 );
function replace_loop_add_to_cart_button( $button, $product  ) {
    // Targeting our product type and checking that the product is purchased by user
    if ( $product->is_type( 'simple' ) && get_webinar_link( $product, true ) && // 'google_meet_webinar'
        has_purchased_product( $product->get_id() ) ) 
    {
        $button = join_webinar_button( $product );
    }
    return $button;
}

代码放在活动子主题（或活动主题）的functions.php文件中。测试和作品。