Discovery Condition AWS Systems Manager

Summary

Without installed and configured SSM agent, AWS EC2 instance can't be discovered via Amazon System Manager.

Affect on Discovery

To discover EC2 instances via System Manager, the SSM agent should be installed on it. When SSM Agent is installed on an instance, it requires permissions in order to communicate with the Systems Manager service.

Resolutions

Install and configure SSM agent on EC2 instance.

At current stage affected VMs can be collected with the search like:
"search VirtualMachine where type in ['AWS EC2 Instance', 'AWS EC2 AutoScaling Group']
show name, type,
#ElementWithCondition:DiscoveryCondition:DiscoveryCondition:DiscoveryCondition.type,
#ElementWithCondition:DiscoveryCondition:DiscoveryCondition:DiscoveryCondition.description,
#ElementWithCondition:DiscoveryCondition:DiscoveryCondition:DiscoveryCondition.impact,
#ElementWithCondition:DiscoveryCondition:DiscoveryCondition:DiscoveryCondition.resolution"

Or you can traverse backward. 

Links

https://docs.aws.amazon.com/systems-manager/latest/userguide/ssm-agent-technical-details.html