my no access message is not showing

Pages are hidden in the top menu for my site as expected using Membership plugin but the problem is the Blogs-Mu theme also have links on the home page, i.e "Find Out More" links that are linked to these hidden pages so when they click on those links they get.

"Sorry, we can't find the content you're looking for at this URL. Please try selecting a menu item from above or to the side of this message to get where you'd like to go."

I will like to use my own custom message instead in the plugin so I tried Edit/Options. I have "protected content page" set to "None". For "Message Title" I have "No Access" then I added a protected message in that box. I thought my message should show in place of the one above.

How do I make this work?

Per the client's request I cannot show the actual site.

Thanks for any help