In some cases, while cross-listing on eBay, you'd see the following error message:
This means that the eBay API does not have the weight and/or dimensions of the product available.
You can either inform eBay Support about this and request that they include it, if they do, it shall auto-populate in Accelerlist.
Or you can simply add it yourself while listing by clicking on this checkbox for 'Update Dimensions' :
This shall enable you to add the dimensions, weight, etc.:
And then you can publish the listing to eBay.