Unworkable product.

[Phenrirr]

Purchased a product that is unworkable. Owner has no contact. How do I complain?

[Rolig Loon]

That's a matter between you and the merchant who sold it to you.  Everybody in SL has a means of contact.  All you have to do is open their profile and send a polite IM or a notecard with your message in it.  Do be patient, of course.  Merchants have RL responsibilities like you and me, and they are not always in world every day, especially during holiday season.  If you don't get a response the first time, wait a few days and send a second polite message.  If you never get a response, and if you bought the item in Marketplace, you can leave a review.  Otherwise, that's the end of it.  Linden Lab will not generally become involved in disagreements between residents.

[Lindal Kidd]

If you cannot find the owner using Search, it's possible that they have left Second Life.  This may have been voluntarily, or they might have been banned by Linden Lab (possibly for selling fraudulent items.)  If so, you're totally out of luck.