Google does not allow some products and content in Shopping ads and listings, and limits others. Google keeps the full lists and updates them, so check its pages for the current rules:
Google's Shopping ads and listings policies (the starting point for all Shopping rules)
Prohibited content is never allowed, for example counterfeit products, dangerous products, and content that enables dishonest behavior.
Restricted content is allowed only with limits, for example alcohol, gambling, healthcare and medicines, and sexual content.
If you sell something in either list, check the policy before you launch. If Google disapproves a product, you will see the reason in your Diagnostics Hub. See How to Use the Shopping Ad Diagnostics Hub.