My archive-posttype.php template is not loading

Question

I'm trying to create an archive-photos.php template for my photos custom post type. The problem I have is that when I view the page it is the archive.php template that is used, not the archive-photos.php. I simply want the archive-photos.php to be used when viewing the archive page for that specific custom post type.

What am I missing here?

Please note at the end that I have set the photos custom post type to be the main loop.

Many thanks for your time and help.

<?php
//custom post type
add_action( 'init', 'create_post_type' );
function create_post_type() {
    register_post_type( 'photos',
        array(
            'labels' => array(
                'name' => __( 'Photos' ),
                'singular_name' => __( 'Photo' )
            ),
        'public' => true,
        'has_archive' => true,
        'rewrite' => array('slug' => 'photo'),
        'menu_position' => 5,
        'taxonomies' => array('genre'),
        'supports' => array('title', 'editor', 'thumbnail', 'post-formats'),
        )
    );
    flush_rewrite_rules( false );
    //this enables post formats.
    add_theme_support( 'post-formats', array( 'image', 'chat', 'video', 'gallery' ) );
    remove_post_type_support( 'post', 'post-formats' );
}
//hook into the init action and call create_photos_taxonomies when it fires
add_action( 'init', 'create_photos_taxonomies', 0 );
//create taxonomy, genres for the post type "photos"
function create_photos_taxonomies() 
{
  // Add new taxonomy, make it hierarchical (like categories)
  $labels = array(
    'name' => _x( 'Genres', 'taxonomy general name' ),
    'singular_name' => _x( 'Genre', 'taxonomy singular name' ),
    'search_items' =>  __( 'Search Genres' ),
    'all_items' => __( 'All Genres' ),
    'parent_item' => __( 'Parent Genre' ),
    'parent_item_colon' => __( 'Parent Genre:' ),
    'edit_item' => __( 'Edit Genre' ), 
    'update_item' => __( 'Update Genre' ),
    'add_new_item' => __( 'Add New Genre' ),
    'new_item_name' => __( 'New Genre Name' ),
    'menu_name' => __( 'Genre' ),
  );    
  register_taxonomy('genre',array('photos'), array(
    'hierarchical' => true,
    'labels' => $labels,
    'show_ui' => true,
    'show_admin_column' => true,
    'query_var' => true,
    'rewrite' => array( 'slug' => 'photos' ),
  ));
}
function my_post_class( $classes ) {
    global $post;
    $terms = wp_get_object_terms( $post->ID, 'genre' );
    foreach ( $terms as $genre ) {
        $classes[] = $genre->slug;
    }
    return $classes;
}
add_filter( 'post_class', 'my_post_class' );
//show posts of post type 'photos', 'page' on home page
add_action( 'pre_get_posts', 'add_my_custom_post_type' );
//make photos custom post type the default post type for the main loop
function add_my_custom_post_type( $query ) {
    if ( is_home() && $query->is_main_query() )
        $query->set( 'post_type', array( 'photos' ) );
    return $query;
}
?>

Answer 1

as determined in the comments, the page URI is ?post_type=photos&genre=boudoir...

The reason why "archive-{$post_type}.php" isn't used in this case is because the page is a taxonomy archive and not a custom post type archive. WordPress is looking for taxonomy-genre.php instead of archive-photos.php, and not finding it, is defaulting back to good old archive.php. Here's a wonderful cheat-sheet on the template hierarchy, which is so useful it's probably worth tattooing on your forearm.