That's only 3 days ago. You can send a second invoice as a gentle reminder to pay or you can open an Unpaid Item case on the 4th day, but I would try the former first because there is a chance you might get paid and dont have to go through the process of reselling.
wait another day then file a complaint about the buyer with ebay and don't ship untl you get paid and verify payment in full
off topic -make sure you always get insurance when you ship packages and you should always require a signature on delivery so the buyer can't complain he got it broken when he signed saying its in good condtion and if ut gets damaged you get paid from the insurance
by the way , it is spelled paid not payed - there is no such word as payed
Don't pester your buyers. Simply open an unpaid item case and let eBay do the talking.
cut him off!