Hi cypha79,
The reason you are unable to post these listings is because your account does not have a valid eBay token, which means your Auctiva account is not linked to any eBay account.
Please generate a new roken by going to Auctiva -> My Account(Tab) -> Ebay Settings, by clicking the "Get NEw Token" link.
Once you have generated an eBay token, you will be able to post these listings successfully without making any changes.
-Mike