And now I have nearly solved it ... however I don't understand what it means :

When I installed the WP site with the EE command, it left the default in /etc/nginx/sites-enabled. This should not be a problem since NGINX should catch my domainname.com and then serve the correct site ... This was not always happening, and it was not happening in a strange fashion ...

After looking at /etc/nginx/sites-enabled/default, I commented out the following :

Default server configuration

server {

    listen 80 default_server;
    listen [::]:80 default_server;   <---------------------IF I COMMENT THIS OUT, THEN IT WORKS !!!

    # SSL configuration
    #

Is this NORMAL behavior for NGINX ? I don't know ... anyone have any comments on this ?