Background: I have developed and managed many WordPress sites over the years. Only one of these sites has this problem, but, based on comments on the WordPress.org forum, others are having the same problem. So far, I have not seen a solution that works.Problem: Links work with the default setting. This setting does not add a .htaccess file to the site. The addresses look like ?page_id=12. Permalinks with just the postname also work fine. But permalinks with the category and the postname throw a Page Cannot Be Found error. WordPress Permalink Options: Plain - default, no .htaccess file createdDay and name - just a radio button choiceMonth and name - just a radio button choiceNumeric - just a radio button choicePost name - this is the equivalent of adding /%postname% in the 6th option. This one works.Custom structure - the code I prefer to use is /%category%/%postname%. This one does not work on this one site. This code does work on all the other sites I have added it to.Environment:The site is hosted on SiteGround.The site is running WordPress 4.6.1The site is using the Matheson theme.There are only 9 plugins that have been checked for being up-to-date.
WordPress permalinks with the category and the postname throw a Page Cannot Be Found error
wordpress;links;permalinks;webpage;link structure
Switch to a default theme and see if that permalink structure works or not. Outdated themes can cause issues with newer WordPress versions.Then after this, try to deactivate one plugin at the time and check the links. One or more plugins are in conflict with structure.Structure where you have just %postname% will work. 