Call me a glutton for punishment but will add this one more time--meaning others will have to follow-up if there are questions.
Please note...deactivate all plugins and switch to the WordPress Default theme. Then in the wp-content/themes/default folder create a file called category.php and put this code in that category.php:
Then visit a parent category to see the results.
As a note, by WordPress standards, ANY category that has been designated a Parent category is not meant to be checked in the category hierarchy when writing posts. Meaning, only the latest generation category should be checked. Think of it like this, only the youngest generation gets the action.
Over and out. Good Luck