What's wrong

Great API, bit I can’t get it to work with my own plugin. What am I doing wrong? (if I echo the $department it is showing the right value that should make $go true, but the theme is not switched)

// Switch to Twenty Eleven theme if the visitor is from a certain department
Conditional_Themes_Manager::register( 'twentyeleven', function() {

	// Get info
	$user       = wp_get_current_user();
	$user_id    = $user->ID;
	$department = get_cimyFieldValue($user_id,"AFDELING");

	if ($department == "Department X") {
		$go = true;
	} else {
		$go = false;
	}

	return (bool) $go;

} );</blockquote>

https://wordpress.org/plugins/wp-conditional-themes/