My sold item is now showing as a new listing

New Member
I listed and sold an item weeks ago. I marked it sold, then this evening I started getting message after message from people wanting to buy it. When I went to view the listing it shows as being posted only hours ago. An error message comes up if I try to mark it sold now or archive it.
Level 9
What does the error message say in full?

In case others are having the same problem and google it, they can maybe find a solution here.