It could be many reasons. It could be unaccepted blog content, spamming or using 301 redirection.
One of the most common culprits is when you migrate your Blogger to self-hosted WordPress.
I know there are many those tutorials with titles like:
"how to migrate blogger to WordPress without losing Google Rank", "How to import a Blogspot blog into WordPress", "Moving from Blogger to WordPress without losing traffic" or something in that line.
Let me forewarn you.
Follow their advice or tips with caution.
According to Google, you CANNOT redirect your Blogger blog to non Blogger website. You can read more in Blogger Help Forum.
Most, if not all Blogger blog owners when they move or migrate their blogs to non-Blogger publishing, they want to retain visitor activity and the so-called "link juice".
Unfortunately, this is not a possibility.
Cannot Redirect Blogger Blog To Custom Domain Outside Google
The point is:
You are not allowed to redirect a Blogger blog to a custom domain addressed outside Google.
You can't redirect traffic from a BlogSpot URL to WordPress.
Blogger does not support "Blogger to WordPress redirection".
The proper and correct way is:
You publish a Blogger blog, and a WordPress blog, simultaneously.
And make a cluster of the two blogs.
Then you need to publicize the move with your readers and get them to update their links everywhere.
You have to deal with the temporary traffic loss, until the blog get re-indexed under the new URL.
As I have warned you before, you could get your site banned by Google search or even got deleted by Google for not following Google Webmaster Guidelines.
Your redirect will eventually get the blog deleted or locked, as a redirecting spam host.
The valid way you can redirect a Blogger blog to a non BlogSpot URL, is using properly setup custom domain publishing - "CNAME" referral.
Or you add your Blogger blog to your new site.
Read this old post by an angry blog publisher, who followed WPBeginner blog post "How to Switch from Blogger to WordPress without Losing Google Rankings".
And see what happened?
He got his blog deleted as spam!
Read this advice and guide by Chuck Croll of The Real Blogger Status.
If you still want to migrate or move your Blogger blog to WordPress with 301 redirection, do it at your own risk.
Google could delete your Blogger blog for migrating to WordPress.