Enabling amazon-ssm-agent in systemd fails on Raspbian

When enabling the amazon-ssm-agent service on Raspbian the expected behaviour is that the service starts on boot.

The actual behaviour is that the service is inactive.
`
user@machineid:~ $ sudo systemctl status amazon-ssm-agent.service
● amazon-ssm-agent.service - amazon-ssm-agent
Loaded: loaded (/lib/systemd/system/amazon-ssm-agent.service; enabled; vendor preset: enabled)
Active: inactive (dead)
`

logs:

`2019-05-31 15:30:36 INFO [MessagingDeliveryService] [Association] Schedule manager refreshed with 0 associations, 0 new associations associated
2019-05-31 15:31:10 INFO [HealthCheck] HealthCheck reporting agent health.
2019-05-31 15:34:55 INFO Got signal:terminated value:0x634078
2019-05-31 15:34:55 INFO Stopping agent
2019-05-31 15:34:55 INFO [instanceID=mi-03162bc76d26788f6] core manager stop requested. Stop type: HardStop
2019-05-31 15:34:55 INFO [HealthCheck] stopping update instance health job.
2019-05-31 15:34:55 INFO [MessageGatewayService] Stopping MessageGatewayService.
2019-05-31 15:34:55 INFO [MessageGatewayService] Closing controlchannel with channel Id mi-03162bc76d26788f6
2019-05-31 15:34:55 INFO [MessageGatewayService] Closing websocket channel connection to: wss://ssmmessages.eu-central-1.amazonaws.com/v1/control-channel/mi-03162bc76d26788f6?role=subscribe&stream=input
2019-05-31 15:34:55 INFO [MessageGatewayService] Successfully closed websocket connection to:%!(EXTRA string=52.119.188.27:443)
2019-05-31 15:34:55 INFO [MessageGatewayService] Ending the channel listening routine since the channel is closed
2019-05-31 15:35:00 INFO Bye.
`

What could be the reason for this behaviour?

Start with the reported systemctl status and logs, then inspect /lib/systemd/system/amazon-ssm-agent.service and how the agent handles termination on Raspbian. Reproduce the enable-and-boot sequence and determine why the service becomes inactive; done means the enabled service remains active after reboot, with a regression test or documented reproduction if the repository provides one.

Written by the indexing model from the issue text.