404 error when including styles on wordpress?

Question

WordPress

Rummaged through everything I can, I can't find a solution :( Help, guys.
Incoming data:
0. Server openserver (nginx + php7), WP latest - 4.7v.
1. Working with a self-made child theme longform-child (parent longform)
2 .The style files that need to be included are in
.../wp-content/themes/longform-child/lp/core
3. I include the following code in (functions.php of the child theme)

function add_custom() {
  wp_enqueue_style('core', get_stylesheet_directory_uri().'/lp/core/core.css', array(), '44');
}
add_action('wp_enqueue_scripts', 'add_custom');

4. What you need is added

... id='core-css'  href='http://my-domain.ru/wp-content/themes/longform-child/lp/core/core.css?ver=44' ...

The path is fully consistent with the one that should be, but when you open the file, a 404 error pops up. There are definitely no typos in the path to the file and the name of the file itself.