Hi cest_tres_chic,
This type of error message is indicative that your listings are unable to be posted because they are missing required information. When an item fails to be posted because it is rejected by eBay, Auctiva will say the item is posting, but an API error will eventually be returned on your "Scheduled Listings" and "Events(red)" pages.
I reviewed the three saved listings in your Auctiva account that had not been posted and found that the aforementioned error is being returned because you neglected to fill in the "zip code" field in the "Checkout Options" section. Once you have filled in this field in each of these listings, you will be able to post them successfully.
Any additional questions or concerns? Please file a support request using the appropriate link on our help page:
http://www.auctiva.com/free-auction-software-help/help.aspx-Mike