/cmd_vel don’t appear and Error during the simulation

Hallo,

I follow the ROS2 tutorial, But the topic /cmd_vel don’t appear

And when I try to run the simulation I get the following error :

2023-01-10 09:15:01 [Warning] [omni.usd] Warning: in SdfPath at line 97 of /buildAgent/work/ca6c508eae419cf8/USD/pxr/usd/sdf/path.cpp – Ill-formed SdfPath <>: syntax error

can anyone help
thank you in advance

that warning shouldn’t stop you from getting messages. Can you confirm that you’ve performed this ROS2 prep step before launching sim and enabling the ROS2 bridge? (where you need to specify the Fast DDS middleware and setting a few env variables): 6. ROS & ROS 2 Installation — Omniverse Robotics documentation