The client lacks sufficient authorization - 404

[serverco]

@mmaedler

There's one last question: How can I generate a certificate that includes both the mydomain.net and www.mydomain.net — if even possible.

Add all the domains you want for that certificate on the command line;

./letsencrypt-auto certonly --webroot -w /var/www/default -d mydomain.net -d www.mydomain.net