This policy applies to Shopping ads and local inventory ads
One or more of your products have been identified as digital books, which are no longer supported for advertising through Shopping ads. Unsupported digital books include, but are not limited to, PDFs, ePub books, MOBI, and 電子書籍. As a result, ads for these products have been disapproved and will stop showing to potential customers.
Physical books, magazines, and audiobooks are still eligible to be advertised through Shopping ads. If any of your products are physical books or audiobooks and have been disapproved on account of being classified as digital books, you can request a review of those offers on the Diagnostics page of Merchant Center.
To stop seeing this issue, remove the digital books from your feed.