This short article give you one of the possibilities that your Hyper-V VM cannot start.
Most of the time when the Hyper-V VM cannot start for more than a minute we turn it off. If you wait 3-4 minutes then you might see the error like I did.
failed to start. Synthetic Ethernet Port (Instance ID 6439BD78-ECE9 435D-8BBF C60873A7163C)
The cause of this is. I removed Hyper-V feature from my Windows 10 and add it back. When you do that then all your virtual LAN ports will lost. You will see the error when you go to the settings of the VM. Create the Virtual LAN port back then it should be fine,