By default, Memberium pages and posts inherit the visibility of their parent page. To phrase it differently, if you cannot see the parent page, then you cannot see it’s child page either.
If this setting is ON, then the parent’s page visibility is required to see the child page.
If this setting is OFF, then the page’s visibility is only determined by its own settings.
You can turn on or off the Page Security Inheritance feature from Memberium -> Settings -> Content Protection screen as shown in the below screenshot…