When a Storage Migration is performed in System Center 2012 Virtual Machine Manager (VMM) on a virtual machine (VM) that is turned off, network settings on the VM are lost. An refresh of the VM following Storage Migration results in the VM no longer being connected to VMM networks and having no networks in the Hyper-V console. You may see in the VMM Admin Console that the VM shows 'Not Connected.'
To work around this issue, rebuild the VM networks for the VM that was turned off after Storage Migration is complete.
for other considerations.