I had a buyer try and register a coin, he just won on ebay

I try and keep a coin in my registry until the new owner gives me feedback. Once I sold a coin on eBay and the new owner decided to list it in his registry right away. He didnt even pay for it!

Another time a guy who bought the coin, listed it on his registry and then returned it to me. When I tried to re-register the coin, NGC would not allow it!?

So when is the correct time to release a coin from your registry?