It requires that the page be indexed, that the page has valid structured data on it, and that our systems have determined that it’s worth showing this structured data.”

So, according to John Mueller, these are the four things to get right to qualify for product rich results:

1. Page must be indexed
2. The page has valid structured data
3. Google’s systems determine that it’s worth showing
4. Submit a product feed

1. Page Indexing

Getting a page indexed (and ranked) can be difficult for some search queries. People who come to me with this kind of problem tend to have content quality issues that can be traced back to using outdated SEO strategies like copying what’s already ranking in the SERPs but making it “better” which often results in content that’s not meaningfully different than what Google is already ranking.

Content quality on the page level and on the site level are important. Focusing on content that has that little extra, like better images, helpful graphs, or content that’s more concise, all of that is so much better than focusing on keywords and entities.

2. Valid Structured Data

This is another area that explains why some sites lose their rich results or fail to get them altogether. Google changes their structured data recommendations and usually the structured data plugins will update to conform to the new guidelines. But I’ve seen examples where that doesn’t happen. So when there’s a problem with rich results, go to Google’s Rich Results Test tool first.