OK, had a look at the instructions for the JTech Inkscape laser plug-in and it looks simple enough. One thing I noted on their overview page is that the program (or plug-in) may need to re-installed if there’s a problem. Hopefully someone else who’s familiar with the JTech unit will be able to give you more help.
Edit to add … Just noticed another thread about the JTech laser and GRBL1.1. Which version of that are you using?
There’s also a Shapeoko FaceBook group with over 800 members where you could ask …