The plugin has removed your category, now there is none category assigned.
As I mentioned before, there has to be a other category assigned otherwise WordPress is so clever to show “uncategorized” when NONE category is assigned to that post.
The way to do is:
First assign the category where it should belong to and then delete “uncategorized”, you will see that there’s only one category left to the posts.
But watch out, de plugin make a new query based on selected category with a different dataset, it can be that the records you changed are on one of the next listing page.
Suc6
Ps. Dont forget to select the check-box, if not there will be nothing happen! In a selected dataset you still can make a selection of wanted records, or all.