This is a drab, nondescript error.
The request could not be processed because the VPN connection is already being started.
The request could not be processed because a VPN connection was already active.
The request could not be processed because the VPN connection is already being stopped.
The request could not be processed because the VPN connection was already stopped.
The request could not be processed because the VPN connection is in the wrong state for this type of request. FIXME: too general?
Invalid arguments were passed with the request. FIXME: too general.
A binary providing the service failed to launch.
The request could not be processed because the VPN connection settings were invalid.