My webhost was telling me that the theme or plugins may be creating a folder called “blog” to be created. So what’s happening is my website.com/blog is showing a 403 error. We keep deleting the folder but it keeps appearing.
Our theme doesn’t create the blog folder. You can temporary activate a default theme on site and check.
I would recommend you to find out conditions for the folder creating, disable all 3-rd party plugins and activate them one by one to find which one creates the folder.
Feel free to ask if you have any other questions.