title: 401 error on CWS Payment Flow
body: <p>My Google Chrome Extension (Annotate for Chrome) has successfully received payments. </p>
  
  <p>I have updated the app recently but not the payment flow. </p>
  
  <p>Now when a user initiates a payment the Google modal pops up (that displays the Google payment - from Buy.js) the spinner just runs endlessly and console shows a 401 error. </p>
  
  <p>I double-checked manifest and in-app purchase SKU etc and don't see any differences from previous versions that worked. My check for current license is working fine - which tells me my app is being recognized by the Google Web Store and returning data on specific users license status...</p>
  
  <p>Any thoughts on what could cause this? Many thanks. </p>
  
  <p>(I submitted a ticket to CWS support - nothing yet). Probably something stupid but I don't know how to debug. Or epic fail on Google's part.</p>