Subcategory 404 issue

I am having an issue with Subcategory pages 404ing.

Desired URL hierarchy:

  • Blog = /blog
  • Category = /blog/CAT
  • Subcategory = /blog/CAT/SUBCAT
  • Post w/ Category as primary = /blog/CAT/POST
  • Post w/ Subcategory as primary = /blog/CAT/SUBCAT/POST

Settings:

  • Blog page is set to be /blog
  • Permalink structure = /blog/%category%/%postname%/
  • Category base = empty
  • Yoast SEO “Remove the categories prefix” = Remove

Everything else is working, except the Subcategory pages are 404ing. And the actual URL that is successfully loading for the Subcategory pages is /CAT/SUBCAT — but this is not what is linked in the sitemap or on the blog posts which are in a subcategory.

I have tried a few different combos of settings, but not successful yet. How can I resolve this issue and get my desired URL hierarchy?

Thank you in advance.