None of the exercises which include this robot appear to be working, The one I have screenshot is Exercise 5.1 but the ones in Exercise 4 didnt make this robot move either. The turtlebot works fine in Exercise 3.
you have to make sure your script is publishing on the right topic.
If your script publishes on a topic called /my_topic, you can check whether it is really publishing by using
rostopic echo /my_topic.
You have to make sure the robot is subscribed to the topic you are publishing.
rostopic info /TOPIC_NAME would tell you whether there are publishers and subscribers.
I have reloaded the exercise pages and re ran the code today and the same code I ran yesterday now works. Maybe there was an issue with the way the exercise loaded yesterday.