Ahrefs says :
The Google Sandbox refers to an alleged filter that prevents new websites from ranking in Google’s top results. Think of it like a probation period—even if you do everything right, your site won’t get decent rankings until it comes to an end.
The Google Sandbox has never been officially confirmed by Google. But many SEOs are confident in its existence, as they see sandbox-like effects when trying to rank new websites.
So what’s the truth? Does the Google Sandbox exist in 2018? If so, how do you prevent Google from “sandboxing” your site?
To answer these questions, I reached out to a few SEO practitioners to learn what they think about Google sandbox in 2018, based on their experience with new websites.
But in our experience there are some cases, our clients’ website got trapped inside the penalty area, which they can not resist fighting.
A Google penalty is the negative impact on a website’s search rankings based on updates to Google’s search algorithms or manual review. The penalty can be a by-product of an algorithm update or an intentional penalization for various black-hat SEO techniques.