I've made several tests. It seems your nw.js-version is not compatible with the plugin. I replaced the old plugin with the latest version, set up the correct parameters and updated the nw.js-version to 0.104.1 (the version I run my tests). Everything works fine.
If you want to check which nw.js-version you are using, type
nw.process.versions.nw
into the console.
If you want to update your nw.js-version, here is a step-by-step-guide to do so.
At the moment I don't know which version you need at least to run the latest version of the GameJolt-Plugin. But I recommend to update to the latest nw.js-version.
You may have to insert a name-property to your package.json. The property is there by default but empty. Just type any name in it.