private static function activate_plugin( $product_id ) {
		// Clear plugins cache used in `WC_Helper::get_local_woo_plugins`.
		wp_clean_plugins_cache();
		$filename = false;

		// If product is WP.org one, find out its filename.
		$dir_name = self::get_wporg_product_dir_name( $product_id );
		if ( false !== $dir_name ) {
			$filename = self::get_wporg_plugin_main_file( $dir_name );
		}

		if ( false === $filename ) {
			$plugins = wp_list_filter(
				WC_Helper::get_local_woo_plugins(),
				array(
					'_product_id' => $product_id,
				)
			);

			$filename = is_array( $plugins ) && ! empty( $plugins ) ? key( $plugins ) : '';
		}

		if ( empty( $filename ) ) {
			return new WP_Error( 'unknown_filename', __( 'Unknown product filename.', 'woocommerce' ) );
		}

		return activate_plugin( $filename );
	}