After copying geometry in 2D, the new geometry does not present the same result in 3D. There are a number of values that can be set on the geometry beyond the line type that help tell ArtiosCAD how the object should be used. These attributes exist because the different rule types used to manufacture the design can be used for different reasons. For instance, a perf may be used to allow someone to easily tear the design or it may be used as a crease. Because of this ambiguity, ArtiosCAD needs some direction on how to interpret and render the geometry.
In the design below, one of the circles was copied from the other, showing the issue. The new circle no longer has the attribute that tells ArtiosCAD that it should be treated as a cut in 3D.
The 3D attributes must be manually applied on the new geometry.
Select the offending geometry.
Open the geometry's properties (double-click the geometry or right-click on the geometry and select Properties).