What does your collision look like for that object? If it’s the orange wireframe landscape, then it’s an invalid collision. https://docs.unrealengine.com/latest/INT/Engine/Content/FBX/StaticMeshes/#collision
When you import, make sure that Auto Generate Collision is not ticked in the the import menu. Also, I had some issues sometimes that collision is not imported when you first import it, but if you then rightclick the model and choose reimport, it would appear.
Regarding collisions for landscapes, you might want to read up on it here: Landscape Collision Guide | Unreal Engine Documentation