Try it like this:
RewriteEngine On
RewriteCond %{HTTP_HOST} !^www. [NC]
RewriteRule ^(.*)$ http://www.example.com/$1 [L,R=301]
RewriteCond %{HTTPS} off
RewriteRule ^(.*)$ https://www.example.com/$1 [L,R=301]
The only real difference here is that first we redirect from non-WWW to WWW then we check for HTTPS and redirect it.
If it does not work, try this one:
RewriteEngine On
RewriteCond %{HTTP_HOST} !^www. [NC]
RewriteRule ^(.*)$ http://www.example.com/$1 [L,R=301]
RewriteCond %{SERVER_PORT} !^443$
RewriteRule ^(.*)$ https://www.example.com/$1 [L,R=301]
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