New sellers of higher priced items are often seeked out by scammers.

I suspect that is the case.

If it has been 4 days, open an unpaid item case which gives the buyer a further 4 days to pay and if they don't then close the case.

Buyer will get a strike, you get a fee credit and you are free to relist.

If the buyer pays, make sure you send with insurance.

Next time, better to list these types of items locally only, no international postage.