two weeks ago, I installed a 3CX on a HyperV for a customer.
The Windows 7-VM where 3CX is installed, got some trouble with its network connection itself.
Specially when moving the VM from one HyperV to another.
In Win 7 and Server 2008, there are those 3 network types, I'm sure you know them (Private Network, Public Network, Office Network). My Win 7-VM messed up them up, and the 3CX Licence was lost.
That's my experience, which leads me to the conclusion that network / internet connection has to be available.