4 days after sale date you can open a non paying case.
I usually send a message asking if there is a problem with payment, then if no response in a day or two, I open the case at 6-7 days.
The buyer then has a further 4 days to pay and if they don't respond, close the case.
You get your fee back, buyer gets a strike and you are free to relist.
To open the case, to the right of the item in your sold list is a small drop down menu.
Select resolve a problem and follow the prompts.
