Verify the solid bodies and their materials.
In the history tree, expand Model / Solids.
Under Solids, branches for copper, Target, and vacuum solid materials are visible.
Expand each branch to see the names of the bodies made of that material. When you click a body's name in the tree, it is highlighted in the modeler window.
Under the Target material, note that there are two bodies, named Target and Target_1. These are the moving bar bodies that will be involved in the co-simulation.