Unit 3.5 laser_scan not sending any messages

Course Support ROS2 Basics in 5 Days (Python)
1

Hello,
When I’m trying to do the unit 3.5 my laser_scan subscrition is not sending anything. I’ve only used the code given in the lesson. When I try to do ros2 topic echo /laser_scan it first says
WARNING: topic [/laser_scan] does not appear to be published yet. When I run the command again it’s just not saying anything anymore. I’ve tried to reset the simulation and to redo the whole unit 3 only with the commands given by the lesson but nothing.
Thank you in advance

2

@simonFerrier
Is the simulation running (without a red dot in the top-left corner? If you could share your entire screen with us, that would help us diagnose the problem more quickly.

First, the topics need to be there:

ros2 topic list