Backend / Admin - Content Boxes is not showing any info at all, no grid, no list, just the title of the page, then blank.

I recently upgraded to version 4.7.1 from 4.7.0 and all seemed to be ok.
I honestly did not check the Content Boxes editing section in the Admin at that point.

Today, I noticed several plugins were out of date, so I updated the plugins today.

Now, today, I cannot see the "Content Boxes" section in admin.
The header comes up, but there are no content boxes listed, not even a grid comes up.

So, it appears something has broken, and I am not sure how to correct.

Anyone have an idea where to look, or how to fix this?

Thanks for the help.