Issue with Error establishing SSH connection to your instance. Try again later.

Recommend using the console to login to instance on the serial console and ensure that SSHd is running and accepting connections. Also look for OS level firewall that might be blocking SSH connections.

I was also getting same error. Let me share here what I did to resolve it

I use gitbash and update the pem file permission --> chmod 400 "myfile.pem"

Then use ssh to connect to the instance --> ssh -i "myfile.pem" ec2-user@instancedetail

After that i was able to connect to my instance using ssh client.

Let me know if that helps.

Based on the information provided, there are several potential causes for your "Error establishing SSH connection to your instance" issue. Let me walk through the most likely problems and solutions:

1. Security Group Configuration: Your security group needs to allow inbound SSH traffic (port 22) from your IP address. If you're trying to connect using EC2 Instance Connect, you also need to allow traffic from the EC2 Instance Connect IP range for your specific region.

2. Network ACL Settings: From your screenshots, I can see that your Network ACL has rules that might be blocking traffic. Ensure that your Network ACL allows both inbound and outbound traffic on port 22 for SSH connections.

3. Instance State: Verify that your instance is fully running and has passed all status checks. A failing status check could indicate an OS-level issue preventing connections.

4. SSH Service: The SSH service might not be running on your instance. Since this is a fresh installation, ensure that the SSH daemon is properly configured and running.

5. Default User: Make sure you're using the correct default user for Red Hat (typically "ec2-user" or "redhat").

6. Key Pair: Confirm you're using the correct private key file when attempting to connect via SSH.

Troubleshooting steps:

1. Update your security group's inbound rules to explicitly allow SSH traffic (TCP port 22) from your IP address and the EC2 Instance Connect IP range for your region.

2. Check your Network ACL to ensure it's not blocking SSH traffic.

3. Try stopping and starting your EC2 instance (not just rebooting).

4. Use verbose mode (ssh -v) when connecting to get more detailed error information.

5. Consider using alternative connection methods like AWS Systems Manager Session Manager if SSH continues to fail.

If you've verified all these settings and still can't connect, it might be worth reaching out to AWS support for more in-depth troubleshooting assistance.
Sources
Failed to connect to your instance Error establishing SSH connection to your instance. Try again later. | AWS re:Post
I am not able to connect my instances by clicking the connect button. | AWS re:Post
wordpress EC2 instance is not connecting through connect option "Connect using EC2 Instance Connect" | AWS re:Post