After setting up a new Role, CPT and capabilities, the new role can't see the featured image

Question

Registering the custom post type:

$labels = array(
  'name' => 'tananyags',
  'singular_name' => 'etananyag',
  'menu_name' => 'E-Tananyagok',
  'name_admin_bar' => 'Add new',
  'add_new' => 'Add New',
  'add_new_item' => 'Add New Item',
  'new_item' => 'New',
  'edit_item' => 'Edit',
  'view_item' => 'View Item',
  'all_items' => 'All',
  'search_items' => 'Search',
  'parent_item_colon' => 'Parent: ??',
  'not_found' => 'No item found',
  'not_found_in_trash' => 'No item found in the trash',
);

$args = array (
  'labels' => $labels,
  'public' => true,
  'publicly_quaryable' => true,
  'show_ui' => true,
  'show_in_menu' => true,
  'query_var' => false,
  'hierarchical'  => false,
  'capability_type'     => array('etananyag','tananyags'),
  'has_archive' => true,
  'menu_position' => 7,
  'rewrite' => array( 'slug' => 'etananyag'),
  'supports' => array( 'title', 'editor', 'thumbnail'),
  'taxonomies'  => array( 'category' ),
  'menu_icon' => 'dashicons-book-alt',
  'show_in_rest' => true,
  'capabilities' => array(
    'edit_post' => 'edit_etananyag',
    'read_post' => 'read_etananyag',
    'delete_post' => 'delete_etananyag',
            'edit_posts' => 'edit_tananyags',
    'edit_others_posts' => 'edit_others_tananyags',
    'publish_posts' => 'publish_tananyags',
    'read_private_posts' => 'read_private_tananyags',
    'read' => 'read',
    'delete_posts' => 'delete_tananyags',
    'delete_private_posts' => 'delete_private_tananyags',
    'delete_published_posts' => 'delete_published_tananyags',
    'delete_others_posts' => 'delete_others_tananyags',
    'edit_private_posts'  => 'edit_private_tananyags',
    'edit_published_posts' => 'edit_published_tananyags',
    'create_posts' => 'edit_tananyags'
        ),
  'map_meta_cap' => true
);

register_post_type('tananyag', $args);

Creating the new role(almost same as author):

    add_role( 'e_tananyag', 'E-Tananyag', array(
    'upload_files' => 1,
    'read' => 1,
    'level_2' => 1,
    'level_1' => 1,
    'level_0' => 1,
  ));

Assigning the new role the custom capabilities:

    $tananyag_role = get_role('e_tananyag');
$tananyag_role->add_cap('edit_tananyags', true);
$tananyag_role->add_cap('delete_tananyags', true);
$tananyag_role->add_cap('edit_published_tananyags', true);
$tananyag_role->add_cap('publish_tananyags', true);
$tananyag_role->add_cap( 'delete_published_tananyags', true );
$tananyag_role->add_cap( 'read_etananyag', true );
$tananyag_role->add_cap( 'edit_etananyag', true );
$tananyag_role->add_cap( 'delete_etananyag', true );

Everything works fine, the user with the role etananyag can see, edit or modify the ctp, but he can't add featured image at all.

Please help

Answer 1

Found the Bug. On the custom post type, the guttenberg editor was activated by : 'show_in_rest' => true. This was blocking the featured image to show up. Removing the guttenberg fix the problem. With the classic editor the featured image is showing on the edit page.