saguaros
This site is live so I had to unpublish the page but I've published one - About which is currently showing now. But if you look at the Main Menu in the backend, there is an About Us which is unpublished in which I get the same error.
UPDATE as of 25 Jul 11:58 AM GMT: Since it is AM here, I've had to unpublish the About page because it's not a good look for my client who trying to re-direct traffic to this new site. However, if you publish it, you'll see that the 404 error exists.
Since I'm using SecurityCheck Pro, you'll need to utilize the site URL which I've updated above to access it.