1. Violation of Shopping Ads Policy.
2. Feed quality violation.
You can read the content in the following official links to ensure that your website complies with the requirements of the Google Shopping Ads Policy https://support.google.com/merchants/answer/6149970?hl=en-Hans&ref_topic=9212502&authuser=0
Because of the above two reasons, you can check the common errors that may appear on the website first according to the description of this document.