Unable to SSH into a machine
If you are on the VPN and you are unable to connect to an instance (it hangs and then
eventually fails with
kex_exchange_identification: Connection closed by remote host),
then the instance is unhealthy. There are probably a number of alerts associated with
the instance too.
You’ll need to sign into AWS and reprovision the instance. You may want to click the “Report instance status” button while you’re there, to inform AWS that the instance is unresponsive - this should help AWS to improve their automated checks in the future.