I have a similar problem. The plugin worked fine but after installing and deleting another plugin related to access levels, this one no longer works. I’ve reset the settings, deactivated/reactivated, uninstalled and reinstalled and reset the settings again. Unregistered users still go straight to a static web page (even though settings say it should be latest posts.) They do get a login screen when clicking on most links but can see everything through the archives links.
I don’t have ip address exceptions of any kind specified.