If you receive the above error message when trying to create a new listing to OnBuy this refers to the barcode that you have entered for this product.
Only ISBN barcodes are permitted when listing under one of the 'books' categories.
If you are using an ISBN barcode for any other category other than the books department the above error message will return.
To resolve this issue you either need to use a different EAN barcode, or you need to change the category that you are trying to list under.
If you have any questions regarding this error message please do not hesitate to contact our support team at firstname.lastname@example.org