AWS Instance Error

Let's start with the networking area.

1. Does the inbound rule for the security group allow SSH?
2. Are the required communications allowed by the network ACLs for the subnet on which the EC2 is running?
3. Is a route to Internet Gateway configured in the route table of the subnet on which EC2 is running?

We also recommend that you review the following document, which describes general troubleshooting methods when you cannot connect to EC2.
https://repost.aws/knowledge-center/ec2-linux-ssh-troubleshooting
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/TroubleshootingInstancesConnecting.html

we may have a long list for troubleshooting (in addition to Riku)

• Check your security group rules to make sure that inbound traffic for SSH (port 22) is allowed from your IP address.
• If your instance is in a VPC, ensure that the associated Network Access Control Lists (NACLs) allow inbound and outbound traffic for SSH (port 22).
• Make sure your VPC has the correct route to the internet. This typically means having a route to an Internet Gateway (IGW).
• Make sure you're using the correct SSH key pair to connect to your instance.
• You can check whether SSH service is running or not
• If you're behind a corporate firewall, it might be blocking SSH connection