Featured images enabled on posts and pages, but not the custom post type

<?php

function theme_styles() {

  wp_enqueue_style( 'bootstrap_css', get_template_directory_uri() .  '/css/bootstrap.min.css' );
  wp_enqueue_style( 'main_css', get_template_directory_uri() .  '/style.css' );

}
add_action( 'wp_enqueue_scripts', 'theme_styles' );

function theme_js() {

  global $wp_scripts;

  wp_register_script( 'html5_shiv', 'https://oss.maxcdn.com/html5shiv/3.7.2/html5shiv.min.js', '', '', false );
  wp_register_script( 'html5_shiv', 'https://oss.maxcdn.com/respond/1.4.2/respond.min.js', '', '', false );

  $wp_scripts->add_data( 'html5_shiv', 'conditional', 'lt IE 9' );
  $wp_scripts->add_data( 'respond_js', 'conditional', 'lt IE 9' );

  wp_enqueue_script( 'bootstrap_js', get_template_directory_uri() .  '/js/bootstrap.min.js', array('jquery'), '', true );

}

add_action( 'wp_enqueue_scripts', 'theme_js' );

//add_filter ( 'show_admin_bar', '__return_false' );

add_theme_support( 'menus' );
add_theme_support( 'post-thumbnails' );

function register_theme_menus() {

  register_nav_menus(
    array(
      'header-menu'   => __( 'Header Menu' )
    )
  );
}
add_action( 'init', 'register_theme_menus' );

function create_widget( $name, $id, $description ) {

    register_sidebar(array(
        'name' => __( $name ),   
        'id' => $id, 
        'description' => __( $description ),
        'before_widget' => '<div class="widget">',
        'after_widget' => '</div>',
        'before_title' => '<h3>',
        'after_title' => '</h3>'
    ));

}

create_widget( 'Front Page Left', 'front-left', 'Displays on the left of the homepage' );
create_widget( 'Front Page Center', 'front-center', 'Displays on the center of the homepage' );
create_widget( 'Front Page Right', 'front-right', 'Displays on the right of the homepage' );

create_widget( 'Page Sidebar', 'page', 'Displays on the side of pages with a sidebar' );
create_widget( 'Blog Sidebar', 'blog', 'Displays on the side of pages in the blog section' );

?>