Netregistry finally got back to me with a fix. And all seems to be working now with .htaccess.
No idea why they wouldn’t do this when I was on the phone with them for hours, or even put the code in their FAQ site. Would have save everyone hours of headach.
Anyway, the code that they provided is:
Enable HTTPS
RewriteEngine On
RewriteCond %{HTTP_NR_SSL} !=“1”
RewriteRule ^(.*)$ https://%{SERVER_NAME}%{REQUEST_URI} [R,L]