I can't get domain.com/blog to come up as the blog

This seems to be the same issue here https://premium.wpmudev.org/forums/topic/blog-page that was unfortunately not resolved.

I can't get cspmgroup.com/blog to display the blog. It will only work if the URL is cspmgroup.com/category/blog. cspmgroup.com/blog redirects to the home page.

In Settings > Reading:

Static page is selected.

Front page: "- Select -" , as in nothing selected (that's the only way it will work)
Posts page: "Blog"

Not sure this is related, but there's a group of widgets called "Sidebar Blog" in the right column in Widgets, yet there is no option in the theme to designate a page as the blog, other than Dashboard > Settings > Reading.