Child Theme not loading parent CSS

Take a look at How to create a Child Theme and you’ll see that:

the previous method to enqueue the parent stylesheet was to import the parent theme stylesheet using @import: this is no longer best practice. The correct method of enqueuing the parent theme stylesheet is to add a wp_enqueue_scripts action and use wp_enqueue_style() in your child theme’s functions.php.

Here’s the example provided:

add_action( 'wp_enqueue_scripts', 'theme_enqueue_styles' );
function theme_enqueue_styles() {
    wp_enqueue_style( 'parent-style', get_template_directory_uri() . '/style.css' );
}