Without the capx or screenshot it's hard to say.
1. What are the names of your products? Aren't they any fancy? I mean some special letters? Spaces?
There was a topic someone struggled with IAP a lot and then it turned out his product name was something fancy and Google couldn't read it. I don't remember the exact rules but to be safe I always use small letters and underscore ("premium_product_1" etc.).
2. Have you set your Google app licence into Cordova IAP plugin settings?
3. Are you trying to test the IAP with the APK from Intel XDK directly or from Google Play?
To test IAP you have to send APK to Google (for alpha testing for instance), then download it as tester and try it out.
1. All they are on my Panel are, 10prm, 30prm, 80prm and 200prm. Nothing fancy, just normal numbers and letters.
2. How do I change the Cordova iAP Plugin settings?
3. Yes I am doing it over Intel XDK - I build it, save it to Dropbox and then manual install on my device. Is that the wrong way? If so, I'll try it the way your just described. [UPDATE] The APK that has the in app purchases and all already in it, is on the Google Play Store. I've released it.