It rather depends on what the case was, where you filed it, and why it closed. If you could provide more detail, that would help get a more specific answer to your situation.
In general, however, if you have filed a case in eBay's resolution center and it has closed, you may be able to file the same or a similar case with PayPal. If you've tried that and it has closed, you could try filing a case with your credit/debit card company, assuming you used one for your purchase.
