If the instance is in a subnet that uses an AWS NAT Gateway, make sure that you're connecting to the instance's private IP address. The instance is unreachable on the public IP address behind the AWS NAT Gateway.
Verify that port 3389 isn't blocked Verify that port 3389 isn't blocked by your AWS security group, Network ACL, OS firewall, or antivirus software.
Confirm you're using the correct firewall and network configuration
- Open a PowerShell window from your local device, and then run the following command:
=> Test-NetConnection -ComputerName yourdomain.exampleco.com -Port 3389 2. In the output of the preceding command, verify that TcpTestSucceeded is True. This indicates that the EC2 instance is responding over the network and you can reach the required RDP port. For more information, see Test-NetConnection on the Microsoft website.
For EC2 checks, refer the below link: https://docs.aws.amazon.com/AWSEC2/latest/WindowsGuide/troubleshoot-connect-windows-instance.html#rdp-issues -- 
solved.... I can't explain but, I'm from non technical field so its very hard to understand me. but after one day of research I solved this problem. first I actually remove my default public IP.(it's trick, search on google/YouTube) then I add a new elastic IP. then I add one new private IP through network interface option. then finally I bind these newly created two IP (elastic + private) together using elastic IP association setting. so now my default IP is already removed. so now I can access my instance through new elastic IP. which is now working like my public IP. that's it DONE.... my all inbound and outbound rules are defaults setting. I never need to edit/change it.
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