Fields are not displayed in custom post type edit form

Hello,

I don't have fields on the edit form for my CPT and I don't understand what is wrong. I created a custom post type with a yeoman template :

  register_post_type( 'so_offer', array(
    'description'          => 'Offre d\'estimation ou devis',
    'labels'               => array(
      'name'               => _x( 'Offres', 'post type general name', 'so_flowbiz' ),
      'singular_name'      => _x( 'Offre', 'post type singular name', 'so_flowbiz' ),
      'menu_name'          => _x( 'Offres', 'admin menu', 'so_flowbiz' ),
      'name_admin_bar'     => _x( 'Offre', 'add new so_offer on admin bar', 'so_flowbiz' ),
      'add_new'            => _x( 'Ajouter', 'post_type', 'so_flowbiz' ),
      'add_new_item'       => __( 'Ajouter nouvelle offre', 'so_flowbiz' ),
      'edit_item'          => __( 'Éditer offre', 'so_flowbiz' ),
      'new_item'           => __( 'Nouvelle offre', 'so_flowbiz' ),
      'view_item'          => __( 'Voir offre', 'so_flowbiz' ),
      'search_items'       => __( 'Rechercher offre', 'so_flowbiz' ),
      'not_found'          => __( 'Aucune offre trouvée.', 'so_flowbiz' ),
      'not_found_in_trash' => __( 'Aucune offre trouvée dans la corbeille.', 'so_flowbiz' ),
      'all_items'          => __( 'Toutes les offres', 'so_flowbiz' ),
    ),
    'public'               => true,
    'hierarchical'         => false,
    'exclude_from_search'  => true,
    'publicly_queryable'   => true,
    'show_ui'              => true,
    'show_in_menu'         => true,
    'show_in_nav_menus'    => true,
    'show_in_admin_bar'    => true,
    'menu_position'        => 10,
    'menu_icon'            => 'dashicons-universal-access-alt',
    'capability_type'      => 'post',
    'capabilities'         => array(),
    'map_meta_cap'         => null,
    'supports'             => array( 'title', 'editor', 'author', 'revisions', 'custom-fields' ),
    'taxonomies'           => array(),
    'has_archive'          => "offers",
    'rewrite'              => array(
      'slug'       => 'offer',
      'with_front' => true,
      'feeds'      => true,
      'pages'      => true,
    ),
    'query_var'            => true,
    'can_export'           => true,
  ) );
}
add_action('init', 'so_register_offer', 15, 0);

And for example, a metabox like :

    $meta_boxes[] = array(
        'id' => 'so_offer_standalone',
        'title' => esc_html__( 'Offre autonome', 'so_flowbiz' ),
        'context' => 'after_title',
        'priority' => 'normal',
        'autosave' => 'false',
        'hidden' => array( $prefix . 'offer_type', '!=' ,'standalone'),
        'storage_type' => 'custom_table',
        'table'        => $wpdb->prefix.'flowbiz_offers',
        'fields' => array(
            array(
                'id' => $prefix . 'customer_registered',
                'type' => 'radio',
                'name' => esc_html__( 'Attribution du client', 'so_flowbiz' ),
                'desc' => '',
                'options' => array(
                    'true' => 'Client enregistré',
                    'false' => 'Client externe'
                ),
                'inline' => true
            )
        )
    );

I don't see any meta box. In the screen options of the edit form (on the top of the screen), there is no custom fields, nor meta boxes checkbox.
I have the extensions MB Custom Table, MB Relationships and MB Conditional Logic activated.
Any idea ?
Is there a hook to check when the meta boxes are added in the edit form ?

Thanks !