Same issue here.
We use google webmaster tools and was checking a few things out then noticed the /category-sitemap.xml was giving a 404 error to google so we checked and yes it was 404.
We then logged into wordpress clicked on seo tab clicked on xml sitemap tab and just clicked on save settings to see if that would fix. It did not and then our strip catagory links where all 404 as well.
Then we clicked on save setting after making sure the button was still checked for removing the catagory/ part of the url’s and now they work again. However the /category-sitemap.xml is still giving 404 error to google.