The filter name is slightly off – use manage_edit-st_kb_sortable_columns
. As for the actual sorting not working, you need implement the logic yourself:
function wpse_208315_sort_by_status( $query ) {
if ( $query->is_main_query() && $query->get( 'orderby' ) === 'statuses' ) {
$query->set( 'meta_key', 'status' /* Post meta field name of status */ );
$query->set( 'orderby', 'meta_value' );
}
}
add_action( 'pre_get_posts', 'wpse_208315_sort_by_status' );