I’m making a non-profit project for a Judo club based on Sparkling theme (maxart.com.pl/ippon), but I got something really wrong as the posts which I add to any of the categories do not show up when I click on the category in the menu. It says ”Oops! The page could not be found”. I switched off all the plugins but it didn’t help. Do you have any idea what could be causing this issue? Thanks in advance.