Only logged in users can access site

Hi I have an intranet site which was using the "members only" plugin to control user access, basically blocking all access unless logged in and redirecting non-logged in users to the login page. For some reason this doesn't seem to be performing it's function as it did before and some aspects of the site are accessible even when not logged in.

I installed the Membership Pro plugin but it seems way too complicated for the features I need and I can't seem to figure out how to set it up to do something similar if it is able to do so.

Can anyone advise if Membership Pro can do as outlined above or if there's another up to date solution which may exist. Thanks