Q:

AWS node Instance can't be accessed

I found problem with my EC2 instance.  The errors messages are like this picture bellow:
enter image description here
Anybody know why could that happen? 

A:

Your Network interface is not up.  Try the below inside your host to check if network interface is up 
ifconfig eth0 up

If not try this and again try the above command
ifconfig eth0 down 

Let me know if you have any issues.