If your post type slug is placement, and you set has_archive to true, then the archive WordPress generates is at /placement/. Set has_archive to placements instead and let WordPress add the rewrite rules (which will also handle pagination properly).
Then, to order by your meta key, add a function hooked to pre_get_posts, check if the query is_main_query() and is_post_type_archive( 'placement' ), then set your meta_query parameters there.