connect to my aws ubuntu from my desktop

I understand you're having trouble connecting to your AWS Ubuntu server from your desktop. Let's go through a few troubleshooting steps to help resolve this issue:

1. Security Group Configuration: The most common reason for connection issues is incorrect security group settings. Ensure that your EC2 instance's security group allows inbound traffic on port 22 (SSH) from your desktop's IP address or from anywhere (0.0.0.0/0) if you're not sure of your IP.

2. Network ACLs: Check if there are any Network ACLs blocking the traffic to your instance.

3. Instance State: Verify that your EC2 instance is in the "running" state in the AWS console.

4. Public IP: Confirm that the IP address you're using (54.174.199.17) is still associated with your instance. Sometimes, stopping and starting an EC2 instance can change its public IP.

5. Key Pair: Ensure you're using the correct key pair (.pem file) that was associated with the instance when it was launched.

6. Firewall Settings: Check if there's any firewall on your desktop blocking outbound connections to port 22.

7. Instance Connect: As an alternative, you can try using AWS EC2 Instance Connect through the AWS Management Console. This can help determine if the issue is with your local setup or the instance itself.

8. VPC Configuration: Ensure your instance is in a public subnet with an Internet Gateway attached to the VPC.

If you've checked all these and still can't connect, you may want to try stopping and starting the instance (note that this may change the public IP address). If the problem persists, you might need to contact AWS support for further assistance.

Remember, for security reasons, it's generally recommended to use a bastion host or VPN for connecting to private instances rather than exposing them directly to the internet.

Sources
problems connection with putty (ssh) | AWS re:Post