[onion2k]

People on ProductHunt are interested in products in general. The cross over between ProductHunt users to <your product> users can, and often is, zero. Getting a ton of traffic from there only means your product is new to people who are interested in seeing new products; there is no reason to believe they're ever going to be customers even if they come and see what you've made.

Not getting any customers from DesignerNews is more of a problem, and probably indicates something is wrong with your call(s) to action. They're obviously not working, or your product isn't useful. Ideally you should have set it up to capture user information before launching, because then you'd be in a position to ask the people who visited why they didn't buy. It's a little late for that now.