You have 32 days to open an unpaid item case unless it's changed in the new MP's.

As jellybird suggests, in future open an unpaid item case when you can. I usually give buyers 5-7 days but closer to 5 days unless I hear from them.

Contact eBay via help at the top and see if they will cancel it or open an unpaid item case for you otherwise you are stuck with the fees.