- Products with an availability attribute of out of stock
- A product URL that links directly to only one relevant item
- Unsecure checkout or a missing refund policy
- Sale of gambling related products such as poker chips
Explanation: Google’s goal is to provide the best user experience on Google Shopping. In order to ensure that the ads Google show to online shoppers are safe, secure, and comply with legal requirements, Google maintain comprehensive enforcement of the Google Shopping policies for all merchants.
Read more here: https://support.google.com/adwords/answer/6103800