I have not received payment for an item I sold and it has gone to the Resolution Centre.

[horses_in_the_manning]

The person who bid and won my item sent me an email four days later saying that they don't want to purchase the item now and that they refuse to pay for it. I opened an unpaid item case. What happens to them? what kind of message do they receive and are there repercussions for them? Also I want to leave negative feedback but it only allows me to choose the positive option, why is this? I am very disappointed that they bid and won the item yet have no intention of paying for it. Any advice?