I really think this is a bug in Nop 3.4. In Nop 3.3, this worked for me with the same configuration.
Now after changing the setting in Nop 3.4, I get this error: "The page isn't redirecting properly. Firefox has detected that the server is redirecting the request for this address in a way that will never complete."
However, after setting the setting to "Pages should have WWW prefix" I did get the site to load again, but it forces redirection to non-WWW site. No setting I set would work other this one, and it did not work per how the setting was stated.
I have Use WWW set for the site, and all sites (but not the store that uses a subdomain).
My results are: http://sitename.com goes to https://www.sitename.com as expected https://www.sitename.com also goes to https://wwww.sitename.com But https://sitename.com goes to https://sitename.com, not https://www.sitename.com
Do I need to do a manual rewrite? I would really rather not as I have two stores on the same domain.
I have tried restarting the application several times.
The problem is also present in the latest release 3.80. If using https, it does not redirect a non WWW to WWW. Example: https://productsforautism.com does not redirect to https://www.productsforautism.com.