add_filter('site-reviews-notifications/notification/is-valid', function ($isValid, $notification, $review) {
    $uid = 'XXXX'; // enter the notification UID here!
    if ($uid !== $notification->uid) {
        return $isValid;
    }
    $user = $review->user();
    if (!$user) {
        return $isValid;
    }
    if (!empty(get_user_meta($user->ID, '_has_coupon', true))) {
        update_user_meta($user->ID, '_has_coupon', 1);
        return $isValid;
    }
    return false;
}, 10, 3);