title: Login with Amazon - Button widget links to error page
body: <p>I'm trying to integrate Amazon's "Login and Pay with Amazon" payment method into my webshop. I followed the steps from the developer docs: <a href="http://docs.developer.amazonservices.com/en_UK/apa_guide/APAGuide_GettingStarted.html" rel="nofollow noreferrer">http://docs.developer.amazonservices.com/en_UK/apa_guide/APAGuide_GettingStarted.html</a></p>
  
  <p>The problems starts at the very beginning. I inserted the code for the head part, and also the button widget (explained in Getting Started > Step 1). But when I click the button in my shop, the popup shows the following error:</p>
  
  <p><img src="https://i.stack.imgur.com/6qJec.png" alt="enter image description here"></p>
  
  <p>It says there is a problem with the handling of my order (although I just expected a login screen). And Amazon is about to fix that problem. But I get this error since the very first time I clicked this button, and that's about a week ago. And I can't find any statements to this error.</p>
  
  <p>Is there anything I could have done wrong? I think I setup everything right (client-id, seller-id, return-url, scope- and popup-parameters). Also the <code>onError</code> function isn't called, so I can't really do any debugging.</p>
  
  <p>What causes the error?</p>