Hello,
Please add this code in your child-theme/functions.php file:
wp_enqueue_style( 'dynamic-css', get_stylesheet_directory_uri() . '/dynamic.css' );
http://prntscr.com/kqreis after that create an empty dynamic.css file in child theme directory.
Then custom css from Theme Options will work fine.
In case it won’t get working, provide temporary FTP access and I will pass the problem to our developers.
Waiting for your reply.
Regards