Hi,
Changing the Render Mode of the surface object from Automatic to Meshes under the Display roll-out should fix the issue. By default, ForestPack doesn’t create a mesh for rendering; it uses a custom shader to generate native instances, allowing millions of items to render efficiently. However, if you want to use a Forest object as a surface for other Forest object(s), a standard mesh must be generated. Note that instancing won’t apply in this case — the Forest object will be converted to a mesh. If your objects have many polygons, you may need to adjust the Display > Max faces limit (default 5 million faces).
Currently, Forest objects cannot be used as items within a ForestSet.
I hope this helps.
Best regards,