As of 31 October, 2017 Google App Engine will no longer support “channels”. The BC2NetLogo tool relied upon this to receive messages from the server. Luckily NetLogo Web is very robust today and is generally a better way to use the Behaviour Composer. For more advanced uses we recommend you use the Download button and open the file in the NetLogo executable program.
Only some documentation pages have changed – the Behaviour Composer is the same – it is just that BC2NetLogo won’t know when the now obsolete “Send to NetLogo” button is pushed.