Our app was SharePoint provider hosted app was developed, published and in use by clients in the Office store since November 2014. It was no smooth process, and took lots of effort and a couple of sessions with Microsoft Support to get it all going, but it was running good, until... some time between 23 December and 5 January. No code updates was deployed to our server, no app updates was published to the store, it just stopped working all by itself.
The error message we are seeing in our logs and front-end, is the well known .net error "Object reference not set to an instance of an object", but the stacktrace reveals it's happening in the TokenHelper class' GetAccessToken() method. This method is called by RenewAccessTokenIfNeeded() - so I'm assuming our access token is trying to be renewed.
Has anyone experienced something similar?
This is high-priority issue for us as our current production application is not working anymore!