Maybe the buyer/seller went on vacation or his internet connection died. Either way you can't complete the trade within the 14 days. Don't worry, relax and take a deep breath.
You can request two more weeks to complete the trade. To do this, go to the item page and click "Request two more weeks" next to the time left counter. The other party will be notified of this action and will be asked to do the same. If he/she does, another 14 days will be added to the counter. Note that this is only possible once, giving you a maximum of four weeks to complete the trade.
But he's on the Bahamas, he can't press the button!
Alright, don't worry. In exceptional cases where you can prove the other party is on vacation or otherwise incapable, but willing, to complete the trade, submit a report and a staff member will review it. If the staff member finds it proven, he/she will add the 14 days to the auction.