layerfx.2.8.py Shadows are not being generated

Hi there,
Thank you very much for the script but I am having problems getting the Bevel and Emboss to generate the shadow portion, it will however generate the highlight. I am running GIMP 2.8.6 on Ubuntu 13.04, I have tried installing and running each one of these versions with no success. I start with a blank drawing with transperant background, fill with any color, draw a box selection and run Layer->Layer Effects->Bezel and Emboss and keeping all defaults click ok, what am I doing wrong?