Instance reachability check failed

Sometimes, a simple restart of the instance can resolve connectivity issues caused by temporary network glitches or misconfiguration. If this step did not resolve the issue, you may need to contact AWS Support for further assistance. They can help you diagnose the issue and suggest additional troubleshooting steps based on the specific details of your instance and network setup.

For ref: EC2 Instance System Logs: This documentation explains how to access and interpret the system logs for EC2 instances, including logs related to instance reachability check failures.

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/instance-console.html#instance-console-get-system-log