It can be a case that the shipping settings that you are trying to push are not compatible with the Google Merchant Center. This is the reason you are getting the above error. You can use flat rate shipping to get approved for the rest of the products.
You can also check the Easy Google Shopping Feed app by AdNAbu, which manages your merchant center feed and other advanced features such as Multilanguage, Multicurrency, and Metafields.
You can also get in touch with our experts and request a demo.
Hope this helps.