1. ROS can't find the package on your path, in which case you need to run rospack profile to update and fix path issues
2. You have not sourced your workspace, in which case you need to add source <path_to_your_workspace>/devel/setup.bash to your .bashrc
1. ROS can't find the package on your path, in which case you need to run rospack profile to update and fix path issues
2. You have not sourced your workspace, in which case you need to add source <path_to_your_workspace>/devel/setup.bash to your .bashrc (then resource your .bashrc or reopen your terminal window)