Hi jean8436,
Since you are receiving an API error stating your token is invalid when you attempt to post your listings, you will just need to generate a new token associating your Auctiva account with your eBay account in order to be able to post those listings successfully. You can generate a new token by clicking the "Ebay Settings" link under the "My Account" tab within your account, and then clicking the "Get New Token" link on the ensuing page.
If you are unable to generate a token for your account, please feel free to contact our customer support team by completing the web form on the following page of our site:
http://www.auctiva.com/help/requesthelp.aspx-Mike