I have built a canvas app that connects to a couple of different office 365 products - sharepoint, groups, etc. Most people are using the app just fine. A couple of users have reported an odd error, though. When they load the app, they get the following error:
Office365Groups.ListGroupMembers failed: {"error": {"code": "InvalidAuthenticationToken", "message":"Access token is empty.", "innerError": {"request-id":"{guid}", "date":"{date}"}}}
This error occurred the first time they loaded the app and hasn't resolved yet. Can somebody please help me understand what is going on here? I'm unable to find anything useful by googling the error message.