This article is intended for Citrix administrators and technical teams only.

Non-admin users must contact their company’s Help Desk/IT support team and can refer to CTX297149 for more information.

When launching an application or desktop session using Citrix Workspace App, the session fails to launch with the error code “Your session 'AppName' did not launch successfully due to error code 3505. Please contact your administrator for more information about the error.”

• You can turn maintenance off for individual machines by going to

Set-BrokerMachineMaintenanceMode -InputObject <domainname>\<hostname> $false

 

• You can turn maintenance off for Delivery Group by going to

Set-BrokerDesktopGroup  <YourDeliveryGroup> -InMaintenanceMode $false

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Problem Cause

For Static Single-session OS machines, the machine assigned to the user, or the Delivery Group is in maintenance mode. 
For Random Single-session OS or multi-session OS machines, the Delivery Group is in maintenance mode.

https://docs.citrix.com/en-us/citrix-virtual-apps-desktops/install-configure/delivery-groups-manage.html#prevent-users-from-connecting-to-a-machine-maintenance-mode-in-a-delivery-group
https://developer-docs.citrix.com/projects/citrix-virtual-apps-desktops-sdk/en/latest/Broker/Set-BrokerMachineMaintenanceMode/
https://developer-docs.citrix.com/projects/delivery-controller-sdk/en/latest/Broker/Set-BrokerDesktopGroup/