The error message you're encountering indicates that the external force and torque being applied in your Simscape Multibody model are not having any effect because the follower port of the 'External Force and Torque' block is rigidly connected to the world frame. In Simscape Multibody, the world frame is an inertial frame of reference, which means it does not move or react to forces and torques.
To apply a force or torque to a solid block in Simscape Multibody, you need to ensure that the force is applied to a frame that is part of the moving body (the solid block) and not rigidly connected to the world frame.
For further information, refer to the documentation links below:
