I struggled with this for the first month that I was selling! I love when customers leave feedback, and I try to leave feedback for everyone else. However, if I was to buy something from another online retailer, I wouldn't necessarily go back and leave feedback on the purchase. The positive feedback does help, but I think people will be confident buying from someone who is making sales and doesn't have negative feedback.
I think you can send them a polite reminder, maybe offer a coupon code. I wasn't getting feedback at first, but I started sending 'thank you' coupon convos as soon as the purchase is made, and I've gotten some feedback now!
