UiPath Orchestrator Guide

Frequently Encountered Orchestrator Errors


Sign out of all RDP sessions on Robot machines before starting a job on them.

The Job Details window displays, among others, the errors that caused a job to fail. Below is a list of frequently encountered errors, and what you can do when you encounter them:

  1. No robot available for user X
    This error is encountered if the username provided for the Robot does not coincide with the one used on the Robot machine. For more information on how to connect the Robot or Orchestrator correctly, see the Connecting Robots to Orchestrator page.
  2. Permission missing: Launcher
    It can occur when you are trying to start a job directly from the Robot machine (from the tray or Studio), and the machine username is not the same as the one used to connect the Robot to Orchestrator. For example, if you connected the Robot to Orchestrator using the ABC username, you cannot start jobs on the Robot from the tray or Studio using a different user, such as XYZ.

If you are sure that the username with which you connected the Robot to Orchestrator is the same as the one on the machine, please use the Regutil.exe tool to deactivate the Robot license and reconnect to Orchestrator. Find more details here.

  1. Logon failure: unknown user name or bad password
    This occurs when you tried to start a job on a Robot for which the credentials (the username and/or password) provided in Orchestrator are incorrect.


If the Robot username is in a domain, the username needs to be in the domain\username format.

  1. Executor start process failed, reason System.UnauthorizedAccessException: Access is denied.
    The error is thrown if the Robot password is not provided. To add the password, edit the Robot, as explained here.
  2. Permission missing: Remote Execution
    This error is displayed if you are trying to run a process on an Attended Robot from Orchestrator.
  3. Executor start process failed, reason: A specified logon session does not exist. It may already have been terminated
    There are two types of occurances:
    A. Every time you try to start the Robot - This means that a logon session cannot be created at the moment. This happens if you are connected to the Robot machine with a different username with RDP. To avoid this error, sign off all the RDP connections on the Robot machine.
    B. Randomly - In this case, you can attempt the following:
    • Check if the Robot machine has enough resources (CPU, Memory).
    • Check the connection time using the mstsc command-line function. If the 60 seconds timeout period expires, the error is displayed.
  4. An existing connection was forcibly closed by the remote host “Ooops! We’re sorry! It seems Orchestrator is down.”
    This issue can occur in the following cases:
    • The server is restarted in Internet Information Services (IIS).
    • The server is shut down.
    • The connection to the server is suddenly lost.
  5. Value cannot be null
    Encountered if, in Orchestrator, you start and kill a job quickly, while the process is still being downloaded on the Robot machine.
  6. Job not found
    The issue occurs when the connection between the Robot and Orchestrator is lost for a scheduled job with the Terminate After option enabled.
  7. The handle is invalid
    This error is displayed in the following cases:
    A. Projects containing UI Automation - when a RDP connection already exists in the background (minimized).
    B. As a known Windows issue.
  8. An attempt was made to reference a token that does not exist
    This error is related to a known Windows issue. For more information, please use the enableLowLevel tracing option and provide the generated .etl file to our support team.
  9. Desktop has been disconnected while performing UI actions
    The issue occurs whenever the RDP connection to the Robot machine is lost. Learn how to avoid this by Executing Tasks in a Minimized RDP Window.
  10. A device attached to the system is not functioning
    This is caused by an external issue.
    "An attached device is not working for one of these reasons: (1) it is switched off, or connected improperly; (2) the floppy disk and drive types are incompatible; (3) the floppy disk is not properly inserted in the drive; (4) the drive door is open; or (5) the floppy disk is not properly formatted."
  11. Executor start process failed, reason System.Runtime.InteropServices.COMException (0x800700AA): The requested resource is in use
    The issue is encountered if the logIntoConsole parameter in the UiPath.settings file is set to true while using High-Density Robots.
  12. Execution error: System.UnauthorizedAccessException: Access to the path 'C:\ProgramData\UiPath…is denied
    This error is encountered in the following situations:
    A. If High-Density and regular Robots write or modify the same file. To avoid this, generate different files for Robots and unique user IDs.
    B. If a Robot does not have write permissions for the target folder.
    C. If the file has been created and the Robot cannot edit it.
  13. Robot already running for user
    This issue occurs when schedules overlap (2-3 schedules start at the same time).
  14. Bad request and The remote host did not answer in a timely manner.
    The issues occur when not all users on a machine are connected as Robots to Orchestrator.

Check the Robot LAN Settings for an enabled proxy server. If a proxy server is specified, check out how Redirecting Robots through a Proxy Server works.


This only works over un-authenticated proxy connections.

  1. The remote certificate is invalid
    This occurs when the public key of the certificate is not imported or it is not imported in the trusted root certification authorities of the local machine. Read about Web Certificates for more information.