If your product barcodes are in the restricted ranges (prefixes 2, 02, 04) or the coupon range (05, 981, 982, 983), than you are not able to advertise products with these barcodes on Google Shopping. Below are the publicly known explenations.
Barcodes starting with 2, 02 or 04
These barcodes are for internal use only, which means not for external sale or not authorized to sell outside of the shop.
Barcodes starting with 05, 981, 982 or 983
These barcodes are coupons or currency coupons.
How to resolve?
As written by Google : Do not include GTIN’s with barcodes beginning with (2, 02, 04, 05, 981, 982, 983). The solution as mentioned by Google’s Documentaiton is to not submit products with these barcodes if you have already done so and Google says it requires a barcode, than in this case you can not submit the products to Google Shopping.