I entered the Workspace ID for the conversation service as described car dashboard app. However, it was deleted somehow during the re-deployment of the app, leading to an error when running it.
I just downloaded cloned the repository, created the service, set the environment variable, and pushed to Bluemix.
The sample worked correctly.
Then I performed another cf push
on my local machine, and the application redeployed from my local machine back to Bluemix.
The sample worked correctly again, and the environment variable was not deleted.
I would suggest putting in your WORKSPACE_ID
environment variable in again and making sure you don't delete your application when you redeploy.