Domain Mapping - No ssl front or backend

Using Let's Encrypt. SSL works on main Multisite site and when using subdomain network site.

When mapping domain and using - I get the SITE NOT SECURE message - mapped site DOES work with http:

Tried htaccess: RewriteCond %{HTTPS} !=on
RewriteRule ^ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301] - Get Error: redirected you too many times.

Thought I read domain mapping would produce ssl if the main site had ssl?