I have an m4.4xlarge instance to which I initially assigned an Elastic IP. The security group of this instance allows SSH access and also allows access to the web app on port 8000. 

Now I clicked on the EC2 instance, chose: Actions > Networking > Manage IP addresses. And then I assigned a new private IP.

Then I created a new Elastic IP address and mapped it to the newly assigned private IP of the network interface. Now I can see in the EC2 instance description that Elastic IPs is showing both old and new Elastic IP. But the IPv4 Public IP field is still showing the old IP address only. 

While I am still able to SSH to the instance using the old Elastic IP, I am not able to do so using the new Elastic IP. Also, I am not able to access the web app on port 8000 using new Elastic IP. How can I accomplish this ?