WordPress’ category URLs, by default, have the URL format:
Your site’s categories have the URL format
So it appears you’ve configured WordPress to remove the word “category” from the category URLs, and whatever you did isn’t working anymore (if it ever worked).
You might want to simply revert your site to the WordPress default category URLs.
Thanks George. Would you give specifics re where/how to do this?
OK George, changing the permalink structure did the trick. Although I’m a little nervous because I’m not sure how I messed this up to begin with. Thanks for your help.