theme 2016 – customize css – nothing happens

Try viewing the page’s source code (ctrl + u, usually) to see if the code is actually being added to the <head> element of the web page. If it is, the problem is not with WordPress, but that you are probably targeting the wrong elements. If so, right-click on the item you are trying to change and select “Inspect” to ensure you are targeting the correct element.

If the code is not being add to the web page, then you may have a plugin conflict which is preventing that. In such a case, disable all your plugins, refresh your browser and server caches, and reload the page. If the code is being added, one of your plugins is preventing WordPress from loading the code.