Hi,
Thanks for letting us know about this, it would appear you have spotted a bug. At present it would appear that before instantiating, you need to switch to a renderer that supports native instancing with RailClone. This could be V-Ray, Corona, or Arnold. After instantiating, you can switch back to any other renderer you like.
Apologies for that, we'll fix this issue so that it's not necessary to switch renderers in future.
Best
Paul