WordPress only includes the post
post type for Category archives by default, but you can add additional post types by altering the query:
function wpse241719_add_custom_types_to_category_archives( $query ) {
if ( ! is_admin() && is_category() && $query->is_main_query() ) {
$query->set( 'post_type', array(
'post',
'work',
// 'another_post_type',
) );
}
}
add_filter( 'pre_get_posts', 'wpse241719_add_custom_types_to_category_archives' );