There is perhaps no frustration in the AWS ecosystem quite like the "TargetNotConnected" error in Systems Manager (SSM). You have an EC2 instance. The status checks are green (2/2 passed). Security groups are locked down, as they should be. Yet, when you attempt to start a session, the console rejects you: "An error occurred (TargetNotConnected) when calling the StartSession operation: The target ... is not connected to SSM." This error is misleading. It implies the instance is offline, but usually, the OS is running perfectly. The issue lies in the communication channel between the SSM Agent and the AWS control plane. This guide provides a rigorous root cause analysis and a step-by-step technical fix for this specific error, moving beyond generic advice to infrastructure-level debugging. The Root Cause: It’s a Pull, Not a Push To fix this, you must understand how Session Manager works. Unlike SSH, where you open a port (22) and "push" a connection to th...
Android, .NET C#, Flutter, and Many More Programming tutorials.