Page Not Found Error with Categories

Hi all:

The categories in the front page produce a “Page Not Found” error and defaults to the following link: https://mysite.org/wordpresscategory/news. I realize the issue lies in /wordpresscategory/. I have spent hours trying to figure this out however to no avail. What am I missing here? Please help. I am desperate.

URL: https://associatedepress.org/wordpress

Thank you all.