You need a 301 redirect like this as htaccess:
RewriteEngine On
RewriteCond %{HTTP_HOST} ^www\.(.*)
RewriteRule ^.*$ https://%1/$1 [R=301,L]
RewriteCond %{HTTPS} off
RewriteRule (.*) https://%{HTTP_HOST}%{REQUEST_URI} [R,L]
There are other alternatives, but that works for me. Just create a new document on the server using your FTP client. Paste in that code and save it as .htaccess
Everything should now default to https://