Sorry about that - we have a cron job that resets the demo user data every few hours. Sometimes if you happen to catch it just at the moment we're resetting, a bug in our code means the demo credentials used by the frontend to log in to the app are stale. If you refresh, you should be okay now :)
Edit: my dev has just issued a fix for this bug, so it will not be a problem going forward!
Edit: my dev has just issued a fix for this bug, so it will not be a problem going forward!