After an overnight sleep :-), the problem has resolved itself.
The problem was that the main home page would not update on the desktop but worked OK on mobile devices. The other web pages would update OK. When the problem was occurring the WP preview page would work OK but if I logged out then the old home page was all I saw. The other symptom was the mobile window showing up on the desktop but that problem also has gone away.
As an FYI, I did check on different browsers and it happened with both Edge and Chrome. I also cleared the browser cache of both browsers with no effect. I also installed a WP plugin to clear any cache on that end but that also did not change anything. Could my hosting company (Bluehost) have been caching the page without my knowledge?