Cannot locate node of type

Hi ,

i take this error when i run roslaunch offboard_py start_offb.launch

i want to run that exam

i have no problem installations (ros noetic, px4)

thank you for your help

ERROR: cannot launch node of type [px4/px4]: Cannot locate node of type [px4] in package [px4]. Make sure file exists in package path and permission is set to executable (chmod +x)

source /opt/ros/noetic/setup.bash
source ~/catkin_ws/devel/setup.bash
source ~/PX4-Autopilot/Tools/simulation/gazebo-classic/setup_gazebo.bash ~/PX4-Autopilot ~/PX4-Autopilot/build/px4_sitl_default
export ROS_PACKAGE_PATH=$ROS_PACKAGE_PATH:~/PX4-Autopilot/Tools/simulation/gazebo-classic/sitl_gazebo-classic
export GAZEBO_PLUGIN_PATH=$GAZEBO_PLUGIN_PATH:/usr/lib/x86_64-linux-gnu/gazebo-11/plugins

hello I have same problem… is it solved?? if solved, please recommend solution??