If you don't receive payment, you can open an unpaid item case in the Resolution Centre as early as 4 days or up until 32 days after the listing ended.

If the buyer doesn't pay, you need to manually close the case in the Resolution Centre within 36 days after the listing ended. If you haven't closed the case on the 37th day after the listing ended, eBay automatically closes it and you don't receive afinal value fee credit. Also, an unpaid item won't be recorded on the buyer's account.

So if you opened a case, you are obviously within 32 days and can close it within 36 days.

Make sure you don't miss the 36th day.