title: Pubsubhubbub - Transient error with every Topic URL
body: <p>We subscribed to YouTube's Pubsubhubbub to get notified if someone published a video on a channel. If we try to look at our Subscription details or the Topic url details through <a href="https://pubsubhubbub.appspot.com/" rel="nofollow noreferrer">https://pubsubhubbub.appspot.com/</a> everything shows a "Transient Error" and the Server returns a 503 Error.
  And it seems to error with every Topic-Url i try. Our Topic Url if it's opened in a browser, however, shows content, so it seems to be right. (<a href="https://www.youtube.com/feeds/videos.xml?channel_id=UCyjzn-6YZur2M-qVwTzbQGA" rel="nofollow noreferrer">https://www.youtube.com/feeds/videos.xml?channel_id=UCyjzn-6YZur2M-qVwTzbQGA</a>)</p>
  
  <p>It worked for a few weeks and yesterday we tried to subscribe to another channel und now this error is everywhere. Even our old subscribe won't get any push notifications anymore and the old topic url returns an error, too.</p>
  
  <p>Anyone knows where the problem could be? Or has the same problem?</p>