Unable to launch EC2 despite shutting down and starting up the instance

I understand your frustration with being unable to connect to your EC2 instance after following AWS's instructions to shut down and restart it. This situation can occur for several reasons, and I'll provide some guidance on how to troubleshoot and potentially resolve the issue.

First, it's important to verify that your instance has actually started successfully. Check the EC2 console to ensure the instance status is "running" and that it has passed all status checks.

If the instance is running but you still can't connect, there are several areas to investigate:

1. Security Group Configuration: Ensure that your security group allows inbound SSH traffic (port 22) from the appropriate sources. For EC2 Instance Connect, you need to allow connections from the EC2 Instance Connect IP ranges for your region, not just your personal IP address.

2. Network Configuration: Verify that your instance is in a public subnet with a route to an Internet Gateway. Check the route table associated with your subnet to confirm there's a route for 0.0.0.0/0 pointing to the Internet Gateway.

3. Instance Network Settings: Double-check that the network settings for EC2 Instance Connect are configured correctly on your instance.

4. IAM Permissions: Ensure you have the necessary IAM permissions to connect to the instance using EC2 Instance Connect.

5. SSH Service: The issue could be with the SSH service on the instance itself. If possible, try to access the instance's system logs through the EC2 console to look for any error messages related to the SSH service.

If you've verified all of these and are still unable to connect, you might consider the following options:

1. Try alternative connection methods: If EC2 Instance Connect and SSH with PEM keys aren't working, you could attempt to use AWS Systems Manager Session Manager if your instance is configured for it.

2. Create an AMI: If possible, create an Amazon Machine Image (AMI) from the instance to preserve its data.

3. Launch a new instance: Using the AMI or your original configuration, launch a new instance to replace the problematic one.

If none of these steps resolve the issue, it may be necessary to contact AWS support for further assistance, as there could be account-specific or regional issues that are not immediately apparent.

Remember, it's crucial to regularly back up your instances to prevent data loss in situations like this. In the future, consider testing the connection immediately after restarting the instance to ensure everything is working correctly before proceeding with your workflow.

Sources
Unable to connect to EC2 Instance | AWS re:Post
Can't SSH into EC2 instance anymore | AWS re:Post

Hello.

What is the status of your EC2 instance?
Are all system checks normal?
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/monitoring-system-instance-status-check.html

It is possible that the SSH process has stopped due to some problem, so why not try restarting sshd using user data?
Please set the user data as below and restart the EC2 instance.
https://repost.aws/knowledge-center/execute-user-data-ec2

Content-Type: multipart/mixed; boundary="//"
MIME-Version: 1.0
 
--//
Content-Type: text/cloud-config; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename="cloud-config.txt"
 
#cloud-config
cloud_final_modules:
- [scripts-user, always]
--//
Content-Type: text/x-shellscript; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment; filename="userdata.txt"
 
#!/bin/bash
sudo systemctl restart sshd
--//--