ui: missing metabox

Where is this metabox (running from add_meta_boxes hook) expected to appear. I can’t find it.

add_meta_box(
      'acf_fb_form_settings',
      'Form Builder Settings',
      array($this, 'acf_fb_main_custom_box_html'),of type callable
      array('acf', 'acf-field-group'),
      'normal',
      'high'
);