This is really great. Worked like a charm for me the first time. I was working in "top" "parallel" view on a floor plan (even though the model is 3D). Instead of having to orbit and go into perspective to make changesI was able to draw right onto the floor plane. Then when I tried it again when drawing a line it didn't lock to the work plane. It drew all over. I'm using Sketchup 2016 on a Mac. Any ideas?

Thank you.