If you're sure the seller acct. is in place (CC on file? Accept Paypal?) what I would try, were it me, is to create similar, which will give a new item number. I'm not really sure about this but it can't hurt
Go to the saved listing-click on the top icon over on the right, everything will come up exactly the same as the original listing, then save it and/or post it. I think this would work, unless there's some requirement missing from the seller account. Be sure to click on 'error check' in Auctiva to be sure there's no missing info that would prevent it from posting.
Let us know if it works, and good luck.