I've been helping another user over on the Sketchup.com forum, and I had to get familiar with the source code for this extension to sort out the issues (I'm not the author). I fixed a couple of bugs that kept it from running on Mac (I don't have a Windows PC, so I don't know whether the fixes were also needed there). In this case the author obviously never tried running it on SU < 2016 so wasn't aware that the trap was mis-coded! TIG packaged my changes into the version on the SketchUcation plugin store.