Voice Client cannot be used if the VPN is in a disconnected state.
When the VPN is in a connected state and if the Voice Client was already loaded with the profile and registered with the PBX:
In such cases, the Voice Client is de-registered with the PBX whenever the VPN is disconnected.
The Voice Client always monitors the VPN status.
Depending on the configuration provided at the Voice Client and Extension Manager end, Voice Client is registered or re-registered with the PBX when the VPN has connected.