user:~/catkin_ws$ roslaunch trajectory_by_name start_service.launch
[start_service.launch] is neither a launch file in package [trajectory_by_name] nor is [trajectory_by_name] a launch file name
The traceback for the exception was written to the log file
Hi @ilinca.sorescu,
Welcome to the community 
This sounds like you forgot to source your setup file after building your workspace, a very common mistake for beginners. After you ran catkin_make you have to run
source ~/catkin_ws/devel/setup.bash
in EVERY shell that you want to use. The setup.bash basically contains all the definitions and locations of your packages. Without that information, your shell doesn’t know where they are.
let me know if that was the issue.
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That solved it. Thank you so much!
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