I set up an AWS EC2 server and then Apache. It works fine.
Cloned the AMI and shared it with another account. Spun up an instance on the new account and it seems to work fine.
I can SSH to the new instance and get a shell. I can get HTTP response on localhost - server config seems fine.
I cannot get a response using the public IP using shell on the instance. Cannot get response from external machine using public IP.
There is no iptables rule to block access.
It appears that the Security Groups are not transferred over when an AMI spins up. (This is logical and actually somewhat comforting.)
So after initializing a new instance from an AMI, it is necessary to edit the Security Group to allow inbound http and https connections.
A response in this article describes how.