Blank pages when viewing Categories on subdomain

I have WordPress installed in a subdomain:
https://mywp.example.com

I also have subcategories:
projects
|__cars

I then choose a custom permalink with the structure /%category%/%postname%/

When I look at posts with a subcategory, I see the url is:
https://mywp.example.com/projects/cars/hello-world (no “category” in URL)

When I click on the category or subcategory to see all posts within that category, I can see the URL as:
https://mywp.example.com/category/projects/
https://mywp.example.com/category/projects/cars/

After enabling this plugin, when I view the post, the URL doesn’t show the subcategory, it just shows:
https://mywp.example.com/projects/hello-world

And when I click on the category or subcategory links, the word “category” is indeed removed from the URL, but there are no pages, just a blank white page.

Any ideas on how to correct this?
Thank you!