Why is PayPal still holding my money for 21 days after I shipped the product? -

I already shipped the product to the buyer, and entered the tracking number information in PayPal. It s more than 4 days and PayPal still have not released the fund! What s going on??? :-(

They have posted fairly promptly to my account.. I don t remember their posted policy, but perhaps they are waiting for the buyer to confirm receipt?