404 page not found

Hi

I have defined multiple categories and subcategories e.g
category
category-1
--subcategory
--subcategory1
category-2

Now I have Joomla article where is defined links pointing to e.g www.domain.com/category-1/subcategory
Quite often when I click that link I get response "404 page not found". When I use Edocman » Categories List menu link, everything is working. After that Joomla article link is also working.
Do You have any idea why I can't use Joomla article links as my first option?
Categories are for registered users only.

Thank You

Hi Harry,
It is Sef urls issue, please go to Edocman Configuration -> Tab: Sef Router Settings and enable configure option: "Insert Category ID"
Thanks
Dam