This is because you copied the path horizontally from where the half-circle profile is located. That doesn’t allow Follow Me to work properly.
Copying the edges to use as the path is a good idea but you should have moved the copy vertically. Then it would be usable as the path.
The edges mentioned in the previous post that were deleted are attached to the model. If you are planning to 3D print the result, you will need to clean that up.
Also, because of the missing faces behind the half circle, Follow Me will create faces that you don’t want. I’ve hidden the top face so the unwanted ones can be seen. Delete those faces and you should have a solid group or component.