What should I do if websites are not getting blocked?

The option under consideration is available for almost all browsers, but the developers recommend installing Google Chrome. While using this browser, you can notice more stable operation of the entire functionality; more correct provision of information about the history of visiting websites; adequate blocking of harmful resources and better filtration of content inadmissible to be viewed by a child.

That's why the specified browser should be given all the requested permissions, while other popular browsers are better off being sent to the permanent black list.