Veeam B&R creates the new adaptor (with settings specified in Virtual Lab properties), however it also forces the old MAC address to be used (as you see in the vmx file of a restored machine), that's why VM fails to power on (as it's expecting to see mac address from VMware range). When the VM is started in the isolated network, Veeam tries to preserve MAC address of the VM by modifying .vmx file of the restored VM and setting up MAC from original machine. If this setting is out of standard VMware range (00:50:56:XX:XX:XX), customer may face this issue. But we can force Veeam B&R to skip preservation of an original MAC Address.