Trying to access modules page callback while authenticated
Make sure you define your new permission using Drupal 7's hook_permission().
Grant your new permission to authenticated user here: /admin/people/permissions/list


Try this:

function mymodule_permission() {
  return array(
    'access mymodule homepage' =&gt; array(
      'title' =&gt; t('Access My Module homepage'),
      'description' =&gt; t('View My Module homepage.'),
    )
  );
}