It is possible to have RED Host Scripts that call external programs or processes and if these scripts are run by the RED scheduler service it can require the service to be able to interact with the Windows desktop. This is normally achieved either by running the service as a user account or by running the services using "Local System" and selecting the option "Allow service to interact with desktop".
However in Windows 8 or Windows Server 2012 onwards by default no services can interact with the desktop. This is true even for services running as Local System with the "Allow service to interact with desktop" option enabled.
This behaviour is controlled by a registry setting. Under the key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Windows there is a value "NoInteractiveServices", which has a default setting of 1. When this is set to 1, no services are able to interact with the desktop, including the RED scheduler service. To change this behaviour to match earlier versions of Windows and allow services to interact with the desktop, this registry value needs to be set to "0".
Any services will also need to be restarted for the change to take effect.