Bricklink problem. Paid the seller by paypal and he just stops responding and it's been 3 weeks. What should I do?

Basically I purchased from bricklink a few sets, paid promptly after getting the quote. He had positive feedbacks only and no negative ones so I thought it should be fine. Now it's been 3 weeks since he last replied me and I've been trying to keep contact but he's not responding. Anyone with experience in this matter? What do I do?