my website is down, I want to know why. Web host is AWS EC2 (us-west-2)

the site is chrisknipp.com
The message when you go to this site now is
Service Unavailable
The server is temporarily unable to service your request due to maintenance downtime or capacity problems. Please try again later.

Apache Server at www.chrisknipp.com Port 443
The web host is AWS EC2 (us-west-2