When trying to start-session, the following error appears:

An error occurred (AccessDeniedException) when calling the TerminateSession operation: User: arn:aws:iam:::user/abc is not authorized to perform: ssm:TerminateSession on resource: arn:aws:ssm:session/abc because no identity-based policy allows the ssm:TerminateSession action

The Fix

It seems that AWS Systems Manager, ssm, requires a separate install after installing the AWS CLI.

https://docs.aws.amazon.com/systems-manager/latest/userguide/session-manager-working-with-install-plugin.html

After installing the Session Manager plugin on your computer, you should no longer have the TerminateSession appear when running StartSession.