Custom block won't display in admin - Drupal 7
Try the next code below, it work for me:

/**
 * implements hook_block_info().
 */
function mymodule_block_info() {
  $blocks['hello-message'] = array(
    'info' =&gt; t('Message'),
    'status' =&gt; TRUE,
    'visibility' =&gt; BLOCK_VISIBILITY_LISTED,
    'pages' =&gt; 'example/1*',
    'cache' =&gt; DRUPAL_NO_CACHE,
  );

  return $blocks;
}

/**
 * implements hook_block_view().
 */
function mymodule_block_view($delta = '') {
  $block = array();

  if ($delta == 'hello-message') {
    $block['subject'] = t('Message');
    $block['content'] = t('Hello World!');
  }

  return $block;
}


See https://api.drupal.org/api/examples/block_example%21block_example.module/7