title: Google Smarthome oauth account linking is not working
body: <p>I have implemented an oauth account linking.<br>
  If I test it with an old cell phone (Android 5.1) it is working.<br>
  On another phone (Android 9) with the same google account it is not working.  </p>
  
  <p>What happens:<br>
  It calls my auth endpoint.<br>
  I redirect to a login page with a google login button.<br>
  After the user is signed in, I called an endpoint on my server which redirects to the google redirect uri.<br>
  On the phone I see very short that he opens the new web site and then the browser is closed.
  Nothing further happens.<br>
  The token endpoint isn't called.</p>
  
  <p>What can be different between this both phones?<br>
  Is there a log where I can see what happens?</p>
  
  <p>With Google Developers OAuth 2.0 Playground the account linking is also working.</p>
  
  <p>Thanks for your help.<br>
  Regards Simon</p>