Code working in functions.php but not in Code Snippets plugin

I guess its to do with when it loads. functions.php loads early.

Yep, more or less. Code Snippets run earlier than the themes are loaded, and you cannot remove an action which hasn’t been registered yet.

Here’s how you can adjust that snippet so it will work:

add_action( 'init', function () {

	//* Remove the site title
	remove_action( ‘genesis_site_title’, ‘genesis_seo_site_title’ );

} );