We are selling downloadable products. These are extensions for ecommerce stores which are tested on all possible versions. We also recommend to purchase support when buying any products if you don't have any experience or website is totally customized.In past experience we have seen most of merchant don't able to install correctly and they don't purchase installation service. When module does not work with wrong installation setting then they ask for refund. So we will not provide any refund in that case until we found the issue why our module is not working.
We strongly recommend to merchants to buy installation service with basic support and changes.