ROS param not appearing

edit

In my launch file I have the line

<rosparam command="load" file="$(find rviz_coco_demo)/config/controllers.yaml"/>

The contents of controllers.yaml is

controller_list:
 - name: arm_controller
   action_ns: follow_joint_trajectory
   type: FollowJointTrajectory
   default: true
   joints:
     - wheel_turn_joint
     - arm2_tele_joint
     - wrist1_lin_joint

After launching my file; I don't see controller_list

rosparam get /controller_list
[]

If I update the launch file to refer to an invalid file name; then I get the below error; so I'm confident this line is running.

RLException: error loading <rosparam> tag: file does not exist [/.../config/xxxcontrollers.yaml] XML is <rosparam command="load" file="$(find rviz_coco_demo)/config/xxxcontrollers.yaml"/> The traceback for the exception was written to the log file

If I manually load the file; it will appear as expected

rosparam load install/.../config/controllers.yaml 

rosparam get controller_list
- action_ns: follow_joint_trajectory
  default: true
  joints: [wheel_turn_joint, arm2_tele_joint, wrist1_lin_joint]
  name: arm_controller
  type: FollowJointTrajectory

Any thoughts on what I am getting wrong in the launch file would be much appreciated!

Thanks]