Import XML on theme activation.

Hi guys. I have the function seen bellow, which I call on theme activation, using the after_switch_theme action:

function herowp_importer_acf(){
	global $wpdb;

				if ( !defined('WP_LOAD_IMPORTERS') ) define('WP_LOAD_IMPORTERS', true); // we are loading importers

				if ( ! class_exists( 'WP_Importer' ) ) { // if main importer class doesn't exist
					$wp_importer = ABSPATH . 'wp-admin/includes/class-wp-importer.php';
					include $wp_importer;
				}

				if ( ! class_exists('WP_Import') ) { // if WP importer doesn't exist
					$wp_import = get_template_directory() . '/inc/plugins/importer/wordpress-importer.php';
					include $wp_import;
				}

				if ( class_exists( 'WP_Importer' ) && class_exists( 'WP_Import' ) ) { // check for main import class and wp import class

						$importer = new WP_Import();

						$theme_xml = get_template_directory() . '/inc/dummy-data/xml/acf.xml.gz';
						$importer->fetch_attachments = false;
						ob_start();
						$importer->import($theme_xml);
						ob_end_clean();
				}

}
add_action("after_switch_theme", "herowp_importer_theme_options");

but nothing imports. I double checked the xml file, and it’s all good. Any ideas?

Regards.