Hello aplusguitars -
I am sorry to hear that you have run into trouble with some listings.
It sounds like you are referring to an API error returned by eBay for some of your listings which is preventing them from posting. The only circumstance I am aware of where that particular message would show up is if you had no Header/Gallery image included in the related saved listing. As those images are required to be able to post to eBay they must be included in the Saved Listing prior to posting.
Typically, when you select an image to be added to a listing you are creating on Auctiva, the Header/Gallery images are automatically selected, however there are ways you can go about creating or modifying a listing you are working on that can create a situation where there is no Header/Gallery image selected, but there are images in a listing.
Please check the actual Saved Listings which have received this API error and ensure that a Header/Gallery image is selected in the Image Selection area of the lister prior to posting them again. If you find that there is a listing which has them that has received this error or you encounter it again after ensuring that your listings have this image data saved to them please continue with your support case or file a new support case letting us know the details and we'll be happy to take a look.