User session not found
When a helpdesk operator wants to start a Remote Assistance session with a user, a request is sent to the user session behind the scenes, so a Remote Assistance invitation is generated and sent back to the operator.
In the machine where the user session is hosted, the Microsoft Remote Assistance executable is executed to generate the invitation file and send it back to the helpdesk operator.
This message indicates that a session for the user could not be found in the computer that is running that session. This could happen if the user logged off before the helpdesk operator accepted the invitation and started the session, for example. The “Start Remote Assistance” job will contain further details about the errors.