Do as Countess says however if you do not wish to relist :

Once the order has been cancelled, you can make a Second Chance Offer to the next highest bidder if you listed using the auction format ( from eBay help)

Here is a link for information on setting up buyer requirements if you haven't already:

https://www.ebay.com.au/help/selling/listings/creating-managing-listings/setting-buyer-requirements?id=4152&st=3&pos=5&query=Setting%20buyer%20requirements&intent=Buyer%20does%20not%20pay&lucenceai=lucenceai&docId=HELP1060

1. You can’t name and shame on these boards. (Take a look at the T&Cs for member-to-member contact and community engagement. A moderator will remove the username.

2. Cancel using the buyer didn’t pay option, once that option becomes available. (4 days?) The buyer will receive an invisible strike as an NPB. Two of those, and he/she will be blocked from buying from every seller who had set up their buyer requirements to block those who have at least 2 strikes.

3. Make sure you have set up your blocks correctly.

4. Also, block this buyer.

5. Do not give the buyer any feedback. Sellers can only give positive feedback, and giving a positive with negative comments is considered bad seller behaviour which eBay will punish if, for instance, the buyer complains to wBay. Moreover, the comment will be removed, leaving only a glowing green for which the buyer clearly doesn’t deserve.

6: Relist.

7. Having done all of the above, relax and forget. It’s not worth anger or worry.