Can't access Facebook campaigns
<p>I'm unable to get a list of my campaigns using Facebook Graph API</p>

<p>Response for <code>/me/adaccounts</code></p>

<pre><code>{
  "data": [
    {
      "account_id": "123456789000001234",
      "id": "act_123456789000001234"
    }
  ],
  "paging": {
    "cursors": {
      "before": "AAAAaaaBBBBcccc",
      "after": "AAAAaaaBBBBdddd"
    }
  }
}
</code></pre>

<p><code>/123456789000001234/campaigns</code> returns</p>

<pre><code>{
  "error": {
    "message": "Unsupported get request. Object with ID '123456789000001234' does not exist, cannot be loaded due to missing permissions, or does not support this operation. Please read the Graph API documentation at https://developers.facebook.com/docs/graph-api",
    "type": "GraphMethodException",
    "code": 100,
    "fbtrace_id": "EilRrOk1CEb"
  }
}
</code></pre>

<p>Note that id's have been changed to dummy-values.</p>

<p>The token is for a system user and the ad account have been assigned to the user (role: admin). Token contains following scopes: <code>read_page_mailboxes, rsvp_event, ads_management, ads_read, read_insights, manage_pages, publish_pages, pages_show_list, pages_manage_cta, pages_manage_instant_articles, business_management, publish_actions</code></p>

<p>What am I doing wrong?</p>