I have the same issue. I have 3 accounts.
1 account posts and shows up on ebay immediately via Auctiva. However the other 2 accounts will take about 12 Hours to show on ebay. Also, the other 2 accounts - if I post directly through Ebay and not Auctiva it will post and shows up on ebay immediately. My account that never has problems is my Power Seller account with alot of feedback. I am not sure if eBay prioritizes Power Sellers or not.
It does drive me nuts to pay for an Auction on ebay and lose a days worth of viewing from buyers.
I sent a support request in. Will let you know if I hear anything interesting back. But will probably be that it takes ebay a while to catalog and put items in the list. But that does not make since when I can do a listing on ebays site and it shows up with no problem?????
Thanks
Tiffany