No force_torque topic is published when loading xacro into ignition gazebo via ros2 launch

I want to simulate the force torque sensor in ignition gazebo together with ros2. I loaded the xacro file to ignition gazebo, the force torque sensor seems to be created successfully, but no force_torque topic is published by “ign topic -l”. If I save the world into sdf file and load it into ignition gazebo, the force_torque topic appears.
The xacro file and launch file are modified from ros_gz/ros_gz_sim_demos at ros2 · gazebosim/ros_gz · GitHub. The two files have been uploaded here: force/torque sensor example & how to add the link information to sensor plugin? · Issue #331 · gazebosim/docs · GitHub
Environment: ubuntu 22.04, ros2 humble, Ignition Gazebo 6.11.0
Thanks for any help!

Partly solved.
For some unknown reason, the <plugin filename="ignition-gazebo-forcetorque-system" name="ignition::gazebo::systems::ForceTorque" /> can not be successfully loaded when written in xacro file.
A makeshift solution is to add this plugin in /usr/share/ignition/ignition-gazebo6/worlds/empty.sdf.

Just for visibility, I have responded to Issue #331 · gazebosim/docs · GitHub.