Hmm, I’m afraid this is probably not the right place to ask for help with this plugin. You are more likely to find help if you ask in the RPG Maker community.
I had a quick look, and I think this post might be relevant.
I find it a bit surprising to read “Tiled changed JSON formatting again in 1.7.x so we have to recreate the plugin from scratch.” I wonder what change they’ve run into.