It sounds like a menu problem. You are likely assigned to multiple menus, and the menu where you've inserted that specific page is lower in the menu list compared to the menu you are currently viewing. Since you can only view one menu at a time, the system displays the first eligible menu in the list, which is why the page from the other menu isn't showing up. To resolve this, you might need to adjust the menu order or ensure that the menu containing your page is higher in the list. Here the KB article about menus
Regarding the page visibility, other than menu related, there aren’t any restriction for Superadmins and Power Users to my knowledge. End Users, however, cannot see that page