How do I leave Feedback for a member who is showing as "not a registered user"?
You can't leave Feedback for a member who is showing as "not a registered user". You'll be able to leave Feedback only if they become registered again within 60 days of the end of the listing. eBay also removes negative and neutral Feedback left by members who later become suspended.
In addition, we don't recommend sending payment to a seller if they are not a registered user.
If you've sent payment to a seller who is now "not a registered user" and you haven't received the item after a reasonable period of time, please file an item not received request from your Purchase history within 30 days of the estimated delivery date..
Learn more about resolving transaction problems in the Resolution Centre or go to the Resolution Centre
If a bidder became deregistered as a user after winning your auction, don't send the item to them until payment has cleared. If they don't send you payment, you can open an unpaid item case in order to claim back your final value fee. As the buyer is no longer registered, you'll be able to close the dispute and request a credit immediately.