Do function.php of child theme has bug?

The contents written in function.php of the child theme is not reflected.

<?php
/**
 * OnePress Child Theme Functions
 *
 */

/**
 * Enqueue child theme style
 */
add_action( 'wp_enqueue_scripts', 'onepress_child_enqueue_styles', 15 );
function onepress_child_enqueue_styles() {
  wp_enqueue_style( 'onepress-child-style', get_stylesheet_directory_uri() . '/style.css' );
}
/**
 * Hook to add custom section after about section
 *
 * @see wp-content/themes/onepress/template-frontpage.php
 */

/*
function add_my_custom_section(){
?>
    <section id="my_section" class="my_section section-padding onepage-section">
        <div class="container">
            <div class="section-title-area">
                <h5 class="section-subtitle"> My section subtitle</h5>
                <h2 class="section-title"> My section title</h2>
            </div>
            <div class="row">
                <!-- Your section content here, you can use bootstrap 4 elements :) -->
                <p>Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Donec odio. Quisque volutpat mattis eros. Nullam malesuada erat ut turpis. Suspendisse urna nibh, viverra non, semper suscipit, posuere a, pede.</p>

            </div>
        </div>
    </section>
    <?php
}
add_action( 'onepress_after_section_about', 'add_my_custom_section'  );
*/

//CSS追加
function add_wp_head (){
 echo '<link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.6.3/css/all.css" integrity="sha384-UHRtZLI+pbxtHCWp1t77Bi1L4ZtiqrqD80Kn4Z8NTSRyMA2Fd33n5dQ8lWUE00s/" crossorigin="anonymous">';
}
add_action ('wp_head','add_wp_head',1);

//Custom CSS Widget
add_action('admin_menu', 'custom_css_hooks');
add_action('save_post', 'save_custom_css');
add_action('wp_head','insert_custom_css');
function custom_css_hooks() {
 add_meta_box('custom_css', '個別CSS', 'custom_css_input', 'post', 'normal', 'high');
  add_meta_box('custom_css', '個別CSS', 'custom_css_input', 'page', 'normal', 'high');
}
function custom_css_input() {
 global $post;
 echo '<input type="hidden" name="custom_css_noncename" id="custom_css_noncename" value="'.wp_create_nonce('custom-css').'" />';
 echo '<textarea name="custom_css" id="custom_css" rows="5" cols="30" style="width:100%;">'.get_post_meta($post->ID,'_custom_css',true).'</textarea>';
}
function save_custom_css($post_id) {
 if (!wp_verify_nonce($_POST['custom_css_noncename'], 'custom-css')) return $post_id;
 if (defined('DOING_AUTOSAVE') && DOING_AUTOSAVE) return $post_id;
 $custom_css = $_POST['custom_css'];
 update_post_meta($post_id, '_custom_css', $custom_css);
}
function insert_custom_css() {
 if (is_page() || is_single()) {
  if (have_posts()) : while (have_posts()) : the_post();
  if (get_post_meta(get_the_ID(), '_custom_css', true) !='') {
   echo "<style type=\"text/css\" media=\"all\">\n".get_post_meta(get_the_ID(), '_custom_css', true)."\n</style>\n";
  }
  endwhile; endif;
  rewind_posts();
 }
}
//Custom JavaScript Widget
add_action('admin_menu', 'custom_js_hooks');
add_action('save_post', 'save_custom_js');
add_action('wp_head','insert_custom_js');
function custom_js_hooks() {
 add_meta_box('custom_js', '個別JavaScript', 'custom_js_input', 'post', 'normal', 'high');
 add_meta_box('custom_js', '個別JavaScript', 'custom_js_input', 'page', 'normal', 'high');
}
function custom_js_input() {
 global $post;
 echo '<input type="hidden" name="custom_js_noncename" id="custom_js_noncename" value="'.wp_create_nonce('custom-js').'" />';
 echo '<textarea name="custom_js" id="custom_js" rows="5" cols="30" style="width:100%;">'.get_post_meta($post->ID,'_custom_js',true).'</textarea>';
}
function save_custom_js($post_id) {
 if (!wp_verify_nonce($_POST['custom_js_noncename'], 'custom-js')) return $post_id;
 if (defined('DOING_AUTOSAVE') && DOING_AUTOSAVE) return $post_id;
 $custom_js = $_POST['custom_js'];
 update_post_meta($post_id, '_custom_js', $custom_js);
}
function insert_custom_js() {
 if (is_page() || is_single()) {
  if (have_posts()) : while (have_posts()) : the_post();
  if (get_post_meta(get_the_ID(), '_custom_js', true) !='') {
   echo "<script type=\"text/javascript\">\n".get_post_meta(get_the_ID(), '_custom_js', true)."\n</script>\n";
  }
  endwhile; endif;
  rewind_posts();
 }
}

//固定ページの改行無効
add_filter('the_content', 'wpautop_filter', 9);
function wpautop_filter($content) {
 global $post;
 $remove_filter = false;

 $arr_types = array('page'); //自動整形を無効にする投稿タイプを記述
 $post_type = get_post_type( $post->ID );
 if (in_array($post_type, $arr_types)) $remove_filter = true;

 if ( $remove_filter ) {
  remove_filter('the_content', 'wpautop');
  remove_filter('the_excerpt', 'wpautop');
 }

 return $content;
}

//固定ページではビジュアルエディタを利用できないようにする
function disable_visual_editor_in_page(){
  global $typenow;
  if( $typenow == 'page' ){
    add_filter('user_can_richedit', 'disable_visual_editor_filter');
  }
}
function disable_visual_editor_filter(){
  return false;
}
add_action( 'load-post.php', 'disable_visual_editor_in_page' );
add_action( 'load-post-new.php', 'disable_visual_editor_in_page' );

I download and use the official child theme.
https://github.com/FameThemes/onepress-child

However, it is not reflected even if it is described in function.php of child theme.
So I have no choice but to edit my parent theme.

Is this a bug?