It's possible that:
* It's a smaller, self-published series: Many authors self-publish works, and these might not be indexed in major databases.
* It's a localized or regional series: The books might be only available in a specific bookstore or area.
* The name is slightly different: Perhaps the series has a similar name, like "Chestnut Hill Chronicles" or something similar. A slight variation in the title could affect search results.
* It's a working title or unpublished series: The series might be in progress and not yet released or published under that title.
To find it, you'd need more information, such as:
* Author's name: Knowing the author is crucial.
* Genre: What type of book is it (romance, mystery, etc.)?
* Any other details about the books: Characters, plot summaries, or even a cover image could help.
With more information, you might have better luck finding the "Chestnut Hill" series.