title: AWS.config.credentials are null between page requests
body: <p>I'm using Facebook to create an authenticated identity via AWS Cognito, that's all working fine and I can login, and synchronise data.</p>
  
  <p>However, if I navigate away from my sign-in page - but remain in my site - the underlying AWS.config.credentials object is then null and I can't synchronise any data via a different page.</p>
  
  <p>Suspect I'm missing something obvious but can't see it from the Amazon docs and don't know what!</p>
  
  <p>Edit: Sorry - should have added - this is via the Javascript SDK</p>