YBYFOODS review for Judge.me Product Reviews App

I used this APP to have reviews on my HTML5 Website. All my products show 0 units, even though my Shopify stock has units on all of them. Can't seem to get past this stage, so basically no way to integrate this widget. I guess the APP is good for Shopify stores, but not for pure integration. They do have an API, but it does not seem to work. The problem can also be on my side, even though I am quite used to integrating APIs of payment gateways, invoice softwares, etc which are usually way more complex. This one is pretty simple, it just does not seem to work. Cheers