In wordpress the Media Library and upload pages do not work if I have anything in my functions.php file in my child theme. I tested this by removign everything, re-uploading to the server and it would load, I then just added the comment <!-- TEST --> with nothing else and the media page would not load.
I went through the steps on This page but nothing worked.
Are you using an opening <?php tag? The WordPress docs say this what should be in a child theme functions.php: https://codex.wordpress.org/Child_Themes#Using_functions.php
If you're doing exactly that then you will need to dig deeper into error logs etc and find out what the exact error being thrown is. Just saying that the pages 'do not work' isn't very descriptive or helpful.