Show Manipulation Trajectory in Rviz

Hello! I use MoveIt! to control a Kuka Youbot arm in Rviz. Apparently i used the computecartesianpath() to move the arm from point A to B. Afterwards i wanted to display the trajetory from A -> B and tried to use the Trajectory Addon in Rviz but it did not work. Do u have any ideas how i can, at least, prove that the youbot operates in a straight line? At least i know, that the computed cartesian path has 144 points and my terminal shows any jointangle for each point when i display the trajectory. Thanks! mutu