Can't update eBay store categories

Hmm! Don't have a real solution, just a suggestion - there is sometimes quite a time lag between doing stuff within eBay and it being picked up by Auctiva - could be a few hours or the next day.
In the meantime, a bit time consuming but would at least get your listings live - why not post the listings with a different store category and then go into the listing in eBay and change the store category to your newly named one? It would mean going into each listing in eBay immediately you've listed it, but could be a temporary working option for you until Auctiva updates itself.
You could also perhaps submit a support request with Auctiva - they are pretty good at responding to them in my experience. If you haven't had cause to do that before, click on the Help button at the top right of this screen, then look to the right of the window, about half-way down is a box headed Customer Support - click on the File a request button and off you go.
Good luck!