Why isn't my site content being protected?

This question is also in the Membership Documentation troubleshooting section, but the answers there haven’t helped. :disappointed: I’ve started by setting up my Stranger access level, but my premium content is only protected when I use negative rules. Positive rules would be much more appropriate for my site structure. What box have I not checked to ensure only my positive selections are visible? I am not signed in as an Admin, and Membership is ‘enabled’.

Thanks in advance!!