title: G Suite Marketplace SDK: The form cannot be saved
body: <p>Sorry for asking this silly question but Google Marketplace SDK UI cannot provide any help with its own form - the configuration form.</p>
  
  <p>I cannot save the form, because it wants something but doesn't say what exactly. I filled out all the Required fields, but it's insisting I need something else - but what?</p>
  
  <p>Any ideas?</p>
  
  <p><a href="https://i.stack.imgur.com/XGczk.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/XGczk.png" alt="enter image description here"></a></p>