Thanks for contacting us. We worked with Chaos Group to resolve a few issues in previous versions of RailClone which involved changes to V-Ray as well as our plugin. As a result V-Ray 1.5, 3.0, 3.1, and 3.2 are no longer supported. Currently supported V-Ray versions are 2.5 and 3.3. If you're already using any of the V-Ray 3.x version upgrading to the most recent version should be free of charge.
I hope that helps, please let me know if there's anything else I can do