CASST0002W Error attaching to region region-name

While attempting to shutdown a region an error occurred trying to attach to the region.
Restriction: This topic applies only when the Enterprise Server feature is enabled.
System Action:
As the shut down program cannot attach to the region the region cannot be shutdown.
Resolution:
Make sure that the region being shutdown is running and retry.
Module:
dfhgrtrm
Destination:
Console