Sorry it works now. Takes a while for Google to create the site map?
Notice that there is no more Edit next to Deactivate under the plugin in the Plugins page anymore. In the older version 4.0.9, there is a Edit.
Thank you.
The Permalink Fix & Disable Canonical Redirects Pack plugin solves the problem. Now, we are able to redirect our custom index.html to WordPress index.php.
https://wordpress.org/plugins/permalink-fix-disable-canonical-redirects-pack/
But not sure of the implications and side effects of this plugin.
The reason why we want our own index.html page is we want a fast static html front page which will load almost instantaneously (so that visitors can see the site loads very fast). This static html will look like one of our WordPress site dynamic page.
