Wordpress Css Child Theme no effect on changes

As I always do with all the themes I use I try to use child themes to customize and not lose these changes with updates. I installed Astra theme for the first time and used your online tool to create the child theme


downloaded the zipped file, extracted and uploaded ftp and activated, everything works fine on the site, but if I try to edit the css file, these changes have no effect on the site. The only way to make changes is to add them directly via customize theme in additional css.

Below is the code present in the functions

 * Flattheme Theme functions and definitions
 * @link https://developer.wordpress.org/themes/basics/theme-functions/
 * @package Flattheme
 * @since 1.0.0

 * Define Constants

 * Enqueue styles
function child_enqueue_styles() {

    wp_enqueue_style( 'flattheme-theme-css', get_stylesheet_directory_uri() . '/style.css', array('astra-theme-css'), CHILD_THEME_FLATTHEME_VERSION, 'all' );


add_action( 'wp_enqueue_scripts', 'child_enqueue_styles', 15 );

Below is the code present in the css file

Theme Name: Flattheme
Author: Brainstorm Force
Author URI: http://wpastra.com/about/
Description: Astra is the fastest, fully customizable & beautiful theme suitable for blogs, personal portfolios and business websites. It is very lightweight (less than 50KB on frontend) and offers unparalleled speed. Built with SEO in mind, Astra comes with schema.org code integrated so search engines will love your site. Astra offers plenty of sidebar options and widget areas giving you a full control for customizations. Furthermore, we have included special features and templates so feel free to choose any of your favorite page builder plugin to create pages flexibly. Some of the other features: # WooCommerce Ready # Responsive # Compatible with major plugins # Translation Ready # Extendible with premium addons # Regularly updated # Designed, Developed, Maintained & Supported by Brainstorm Force. Looking for a perfect base theme? Look no further. Astra is fast, fully customizable and beautiful theme!
Version: 1.0.0
License: GNU General Public License v2 or later
License URI: http://www.gnu.org/licenses/gpl-2.0.html
Text Domain: flattheme
Template: astra

What could be the problem? Thank you in advance for any suggestions