If you’re making a custom post type archive template – archive-custom_post_type_name_here.php – and it’s not working (i.e. the standard archive.php template is still being used) and you think that you’ve exhausted all options… make sure that you’re not viewing a custom taxonomy term and expecting the archive template to be used! In this instance, the custom template that you need is taxonomy-custom_taxonomy_slug_here.php