"When you export something you have to have a commercial invoice showing the value, buyer, etc. UPS should have requested that you fill this out when you shipped your stuff. You can find a blank form to fill out at-- https://www.ups.com/intl_forms?OriginCou… --You'll need to fill out, sign & send this to UPS, you can call them at 800-PICK UPS to get a contact of who to send this to. If not it could be delayed for a while in customs. You may also need to complete a NAFTA which you can get from that site too."
In this case I'm the buyer. I'm not sure how much of that I can do, as the recipient. I PM'd the seller, but he's sold here before so I think he would know this was needed.