Gen 2 VM - Setting the Boot order in Powershell does not work

Hyper-v 2012 R2

I'm using the following command to set the Boot Order for Gen 2 VM however when the VM is powered on, it continues to boot from the OS boot drive SCSI,0,0

Set-SCVirtualMachine -VM "My-VM" -FirstBootDevice "SCSI,0,1"

I've confirmed that "SCSI,0,1" is set as the DVD drive and this is indeed a Virtual DVD that has an ISO mounted on it.

Any ideas why this is being ignored?