The system license is associated with the MAC address of the primary network interface. By default, HyperV will randomly assign the MAC address on each guest VM on bootup. If you move a Mitel Linux HyperV guest to a new host, copy the MAC address from the exiting host (or if you do a live migration, HyperV should do this for you), and change it to a static assignment. Worst case, go into Mitel AMC and clear the hardware ID, then re-synch from the new host.