Child theme not working

Hi! Apologies if this is a very novice question, but I’m just getting started with WP. I’m using Optimizer (free) theme on my site and created a child theme. I saved the child directory in /themes, added style.css and functions.php. I was able to active the child theme in the WP dashboard, and everything looked the same (except that the background color on all the pages was different, but I was able to customize that using my theme). This suggested to me that the child theme was working, but then when I pasted some code into the style.css, nothing seemed to be happening. My style.css looks like this:

*/
Theme Name: Amy's Child
Description: Child theme for Optimizer (23/06/2016)
Author: Amy
Template: optimizer
Version: 1.0.0
*/

body.page-id-64 {
 background: #ffffff;
}

.blog .container > .row {
background: white;
}

My functions.php is:

<?php

add_action( 'wp_enqueue_scripts', 'optimizer_enqueue_styles' );

function optimizer_enqueue_styles() {
   wp_enqueue_style( 'parent-style', get_template_directory_uri().'/style.css' );
}
?>

Am I doing something wrong?

Thanks so much in advance!