Redirection plugin fail, resulted in a 404

I installed Redirection and followed the directions to bulk upload.

This was for a bulk upload of old blog posts that we want to redirect to main blog page for this site. The redirect url was therefore as follows: /blog

The result is that all the blog posts we wanted to redirect are going to a 404 page.

Here is an example: https://www.peabodysmith.com/blog/landscaping-tips-bretton-woods-real-estate-owners

I should say that the website https://www.peabodysmith.com is not a WordPress site–but it has a WordPress blog. Would that make a difference in using Redirection?