Systems Manager Fleet Manager does not have SSM-SessionManagerRunShell document

Hello.

According to the documentation, "SSM-SessionManagerRunShell" is automatically set up when using a session manager.
https://docs.aws.amazon.com/systems-manager/latest/userguide/getting-started-sessiondocumentaccesscheck.html

When you configure Session Manager for your account, the system creates a Session type document SSM-SessionManagerRunShell. This document stores your session preferences, such as whether session data is saved in an Amazon Simple Storage Service (Amazon S3) bucket or Amazon CloudWatch Logs log group, whether session data is encrypted using AWS Key Management Service (AWS KMS), and whether Run As support is allowed for your sessions. The following is an example.

Also, looking at the questions below, it seems like this is a temporary issue and will be resolved over time.
https://serverfault.com/questions/1143873/aws-ssm-invaliddocument-document-with-name-ssm-sessionmanagerrunshell-does-not

I had the same issue today.. Before you can set a password for your new user, AWS KMS encryption must be enabled in your session preferences.

I had to enabled KMS in Session Manager Session Preferences. You will require a Customer Manged KMS key that SSM and Users can use

https://docs.aws.amazon.com/systems-manager/latest/userguide/session-preferences-enable-encryption.html