Need some help with an events page 404

Ok, like many I was looking to adjust the category and slug of the events permalink structure, I was successful using these 2 pieces of code.

/**
 * Customize advert post type slug
 *
 * @link https://github.com/simpliko/wpadverts-snippets/blob/master/custom-slugs/custom-slugs.php
 */
add_action( 'adverts_post_type', 'customize_adverts_post_type' );
function customize_adverts_post_type( $args ) {

  if ( ! isset( $args["rewrite"] ) ) {
    $args["rewrite"] = array();
  }

  # adverts_post_type hook is used for multiple post types, we only want to affect 'advert'
  if ( ( ! isset( $args['taxonomies'] ) ) || ( ! in_array( 'advert_category', $args['taxonomies'] ) ) ) {
      $args["rewrite"]["with_front"] = false;
      return $args;
  }

  $args["rewrite"]["slug"] = "classifieds/%advert_category%";
  $args["rewrite"]["with_front"] = false;
  $args["rewrite"]["feeds"] = false;
  $args["rewrite"]["pages"] = false;

  return $args;
}

/**
 * Customize advert_category taxonomy slug
 *
 * @link https://github.com/simpliko/wpadverts-snippets/blob/master/custom-slugs/custom-slugs.php
 */
add_action( 'adverts_register_taxonomy', 'customize_adverts_taxonomy' );
function customize_adverts_taxonomy( $args ) {
  if ( ! isset( $args["rewrite"] ) ) {
    $args["rewrite"] = array();
  }

  $args["rewrite"]["slug"] = "classifieds";
  $args["rewrite"]["with_front"] = false;
  $args["rewrite"]["feeds"] = false;
  $args["rewrite"]["pages"] = false;

  return $args;
}

/**
 * Expand %advert_category% in permalink structure.
 *
 * Adapted from https://shibashake.com/wordpress-theme/add-custom-taxonomy-tags-to-your-wordpress-permalinks
 */
function customize_adverts_category_permalink( $permalink, $post_id, $leavename ) {
    if ( strpos( $permalink, '%advert_category%' ) === FALSE ) return $permalink;

    // Get post
    $post = get_post( $post_id );
    if ( ! $post ) return $permalink;

    // Get taxonomy terms
    $terms = wp_get_object_terms( $post->ID, 'advert_category' );
    if ( ! is_wp_error( $terms ) && ! empty( $terms ) && is_object( $terms[0] ) ) {
        $taxonomy_slug = $terms[0]->slug;
    } else {
        # we can't just remove the slug or the post name is matched as
        # a category name and we get a not found error
        #return str_replace( '%advert_category%/', '', $permalink );
        
        # try to default to first category in the taxonomy
        $terms = get_terms( array(
            'taxonomy' => 'advert_category',
            'hide_empty' => false,
            'orderby' => 'term_id',
        ) );
        if ( ! empty( $terms ) && ! is_wp_error( $terms ) ) {
            $taxonomy_slug = $terms[0]->slug;
        } else {
            # default category slug
            $taxonomy_slug = 'for-sale';
        }
    }

    return str_replace( '%advert_category%', $taxonomy_slug, $permalink );
}
add_filter( 'post_type_link', 'customize_adverts_category_permalink', 10, 3 );

/**
 * Set default advert_category for adverts.
 *
 * This function sets a default category for any advert if unset
 * (match the default category set in the permalink above).
 */
function customize_adverts_default_category( $post_id, $post, $update ) {
    $slug = 'advert';
    if ( $slug != $post->post_type ) {
        return;
    }

    $terms = get_terms( array(
        'taxonomy' => 'advert_category',
        'hide_empty' => false,
        'orderby' => 'term_id',
    ) );
    if ( ! empty( $terms ) && ! is_wp_error( $terms ) ) {
        wp_set_object_terms( get_the_ID(), $terms[0]->term_id, 'advert_category' );
    }
}
add_action( 'save_post', 'customize_adverts_default_category', 10, 3 );

/**
 * Add rewrite rules for adverts url structure.
 */
add_action( 'init', 'customize_adverts_rewrite_rules' );
function customize_adverts_rewrite_rules() {
    global $adverts_rewrite_rules_added;
    $adverts_rewrite_rules_added = 0;

# force flush_rules() for testing (FIXME: disable for production!!!)
if ( 1 ) {
    global $wp_rewrite;
    $wp_rewrite->flush_rules();
}

    # rewrite rule for per-category feed
#
# the generated feed isn't right (the <span> containing each 
# advert title is outside the <a> link), disabled until fixed.
#
#    add_rewrite_rule(
#        'classifieds/([^/]+)/(feed|rdf|rss|rss2|atom)/?$',
#        'index.php?advert_category=$matches[1]&feed=$matches[2]',
#        'top'
#    );
#    $adverts_rewrite_rules_added++;

    # todo:  add rule for classifieds/feed (all categories)

    # rewrite for individual advert
    add_rewrite_rule(
        'classifieds/([^/]+)/(.+)/?$',
        'index.php?advert=$matches[2]',
        'top'
    );
    $adverts_rewrite_rules_added++;

    # rewrite for category
    #
    # The 'add' and 'manage' pages would be masked by this rewrite,
    # so we exclude those in the regex: (?!add|manage)
    #
    # get post object for 'Default Ads List Page' set in wpadverts options
    if ( function_exists( 'adverts_config' ) ) {
        $post = get_post( adverts_config( 'config.ads_list_id' ) );
    } else {
        $post = get_page_by_path( 'classifieds' );

        if( is_null( $post ) ) {
            $post = get_post( 3917 ); # actual page id via manual lookup
        }
    }

    $add_post = null;
    $manage_post = null;

    # get post object for 'add' and 'manage' pages
    if( ! is_null( $post ) ) {
        $add_post = get_page_by_path( $post->post_name . '/' . __( 'add' ) );
        if( is_null( $add_post ) ) {
            $add_post = get_post( 3918 ); # actual page id via manual lookup
        }

        $manage_post = get_page_by_path( $post->post_name . '/' . __( 'manage' ) );
        if( is_null( $manage_post ) ) {
            $manage_post = get_post( 3919 ); # actual page id via manual lookup
        }
    }

    $exclude = 'feed|rdf|rss|rss2|atom';

    if( ! is_null( $add_post ) ) {
        $exclude .= '|' . $add_post->post_name;
    } else {
        $exclude .= '|add';
    }

    if( ! is_null( $manage_post ) ) {
        $exclude .= '|' . $manage_post->post_name;
    } else {
        $exclude .= '|manage';
    }

    add_rewrite_rule(
        'classifieds/((?!' . $exclude . ')[^/]+)/?$',
        'index.php?advert_category=$matches[1]',
        'top'
    );
    $adverts_rewrite_rules_added++;

}

/**
 * Clean up rewrite rules.
 */
add_filter('rewrite_rules_array', 'customize_adverts_cleanup_rewrite_rules');
function customize_adverts_cleanup_rewrite_rules( $rules ) {
    global $adverts_rewrite_rules_added;
    $cnt = 0;

    foreach ( $rules as $rule => $rewrite ) {

         # remove rewrite rules containing '%advert_category%'.
        if ( strpos( $rule, '%advert_category%/') !== false ) {
            unset( $rules[$rule] );
            continue;
        }

        # remove all default rules -- no, this kills %adverts-payment% rules
        #if ( strpos( $rule, 'classifieds/') === 0  &&  $adverts_rewrite_rules_added <= $cnt++ ) {
        #    unset( $rules[$rule] );
        #}

        # remove conflicting default rule
        if ( $adverts_rewrite_rules_added <= $cnt++ && strpos( $rule, 'classifieds/([^/]+)/?$') === 0 ) {
                unset( $rules[$rule] );
        }

    }
    return $rules;
}

The only problem now is that pages I made children of my main classifieds page are now showing a 404.

My main page is: https://inthebunch.co.za/classifieds/
And one of the 404 pages is: https://inthebunch.co.za/classifieds/post-an-ad/