Ebay rolled out several new changes recently that seriously affected creating new listings or using saved listings on Auctiva. Ebay changed many category numbers AND they now require product identifies on new listings such as ISBNs or MPNs.
If you list using profiles in Auctiva, you have to back into those profiles and RE-ENTER the category if you had one chosen before - just start all over and it will insert the new number. Then you can create new listings. When doing that, if the product is not found in the eBay catalog, yes, you should be able to choose "not found" or "unknown" or whatever the exact wording is.
You cannot use saved Auctiva listings at all to edit or relist from without redoing the product and its category due to the way Auctiva dealt with the change imposed by eBay. Unfortunately the system thinks we have new categories, when, in fact, the software should just recognize the old number and change the number without losing all the saved data, but it is not working that way. If you need to edit/use saved listings, you'll have to update the category and product details, which is a super hassle if you have thousands of listings, many with customized specifics that you have entered manually. It means redoing it all.
Best of luck. All of us are affected by these two major changes on eBay, and those that list in categories that had their number changed have a double problem to deal with.