eBay The UPC/ISBN field is missing. ErrorCode: 21919301

Cause

Since ISBNs/UPCs are not mandatory on eBay (excluding certain product categories, such as books), error 21919301 is probably due to an incorrect category placement. 

Solution

Make sure you have left the barcode field blank and retry.

Alternative Solution

Try editing the listing and publishing it by changing the category. You should change the category. To do it:

• Open the Product Tab

• Click on the product in error

• Click on “Edit”

• Choose a category similar to the one you were trying to list your product in, and type it in the category field.

• Click on save.

If you succeed in publishing it you can change the category on eBay soon after.