This eBay error can occur if you are using Australia Post Calculated Postage on your eBay postage policy e.g.
To use Calculated Postage on eBay it means you must supply the package weight and dimensions of a product to correctly calculate the postage cost for an item.
As a first step, ensure that any products affected by this error have the weight and dimensions in our platform e.g. on the Product Details page, you should see the following type of data showing:
Note: Unfortunately, for merchants using Shopify, we are unable to import product dimensions via the Shopify API. There is a workaround for this that requires the use of Shopify Meta fields.
By setting up dimension data through Meta Fields in Shopify (length, width and height values) and mapping them within Omnivore, we are then able to send the necessary information that eBay require.
Please see here for steps on how to set up Shopify Meta Fields
If your product weight and dimensions are correctly imported into Omnivore, the error may be caused by one of two things: either you have enabled International Postage, or the dimensions do not meet Australia Post’s minimum size and weight requirements for the service you selected.
For International Postage: Try temporarily disabling it to see if the error clears. If it does, the issue is likely that the selected international service only accepts items within certain size limits. You can then try selecting a different international service that supports your product dimensions.
For domestic shipping or if the above doesn’t work: Check the minimum size and weight requirements for the Australia Post service you are using. Ensure the dimensions and weight entered for your product meet or exceed these minimums.