title: Dynamic notify_url not called
body: <p>I don't want to create a duplicate question but I cannot find anything similar even though the title is pretty common here :)</p>
  
  <p>Long story short, I'm passing a notify_url for a buy button, the url is public under a .com domain (i can access it using GET/POST) but for some reasons the paypal sandbox does not call it after a test payment is done.</p>
  
  <p>At this moment the only logic I have under the call back is to save the call in a database for logging purpuses so I can clearly see it is not called at all.</p>
  
  <p>I tried to activate/deactivate the IPN notification in my profile and it did not affect the results.  Still not call.  </p>
  
  <p>In the IPN history I can see it; in retrying phase and eventually it became Failed.  The callback is correct, no HTTP response code however - it's like the call is not done or the URL is not accessible.  But again, the URL is public hosted on azure so not a localhost or something :p</p>
  
  <p>This is how the button code looks, I'd appreciate any feedback you may have as this is really frustrating. I replace the original site address and business name for privacy reasons.</p>
  
  <p>Can you pls advice if there's any setting that I may be missing?</p>
  
  <pre><code>&lt;form action="https://www.sandbox.paypal.com/cgi-bin/webscr" method="post" target="_top"&gt;
  &lt;input type="hidden" name="cmd" value="_xclick"&gt;
  &lt;input type="hidden" name="notify_url" value="http://beta.example.com/callback/paypal"&gt;
  &lt;input type="hidden" name="return" value="http://example.com"&gt;
  &lt;input type="hidden" name="business" value="xxxx@example.com"&gt;
  &lt;input type="hidden" name="lc" value="US"&gt;
  &lt;input type="hidden" name="item_name" value="INVOICE 111"&gt;
  &lt;input type="hidden" name="amount" value="20"&gt;
  &lt;input type="hidden" name="currency_code" value="USD"&gt;
  &lt;input type="hidden" name="button_subtype" value="services"&gt;
  &lt;input type="hidden" name="no_note" value="0"&gt;
  &lt;input type="hidden" name="bn" value="PP-BuyNowBF:btn_buynowCC_LG.gif:NonHostedGuest"&gt;
  &lt;input type="image" src="https://www.paypalobjects.com/en_US/i/btn/btn_buynowCC_LG.gif" border="0" name="submit" alt="PayPal - The safer, easier way to pay online!"&gt;
  &lt;img alt="" border="0" src="https://www.paypalobjects.com/en_US/i/scr/pixel.gif" width="1" height="1"&gt;
  </code></pre>
  
  <p></p>