eBay Weight or Dimensions are Missing
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.