Apache not listening on port 443

Did you enable mod_ssl? Since you're running Debian, this is the way to do it (run as root, or via sudo):

a2enmod ssl

Port 443 is HTTPS. From your netstat output:

tcp6       0      0 [::]:https              [::]:*                  LISTEN

It is clear that a process is listening on port 443. To confirm whether the above is Apache (httpd) process, it is important to run the command as root. Use ss instead as netstat is deprecated:

# ss -tlnp