Menu problems on localserver

Greetings.
I am working on a new site on my localserver, using WAMP. I have to be honest and admit that this is my first attempt at creating a site this way. The reason is that I am creating for a good friend who has yet to provide me with his domain access.
I am using Advertica Lite and, until today, had no issues when editing the default home page. I created a “Main Menu” and assigned it in the customizer. I then created three new pages and began editing one of them. So far, so good.
Following my first page edit and update, I tried to view the page. All I get is a 404 page not found error. Everything seems to be as it should. I must be missing something but, for the life of me, I cannot see what it is.
Can anyone point me in the right direction, please.
Many thanks.