Hyper-V NIC Removal - Fails to Start

Remove the vNIC in the virtual machine's properties within Hyper-V Manager.
Apply & OK.
Use the Add Hardware to add the "old" vNIC.

Once done you can delete the virtual switch that was associated with the new removed physical network adapter.

does this machine need to connect to the network before login?
in
try switching the network virtual switch in the network adapters and see if the failure to boot follows

Philip - Let me better explain. I have a VM that I added a second Network Adapter under the Settings of the VM because I wanted to Team the NICS, which I did successfully. However, I no longer need the TEAM so I broke it and don't need 2 Network Adaptors for that VM anymore and want to remove the second Network Adapter. So... I did just as you said, I went in and removed the Network Adapter from the VM so it only had one. When I do that, the VM will reboot fine, but if I actually shut it off and then try to turn it back on it immediately kicks up an error like below. But If I go into Add Hardware and readd the Network Adaptor I just deleted it will fire back up. I can't seem to get rid of the unneeded Network Adaptor without breaking the VM.

Well that's terrifying! OK I'll export it as is and then give it a go. Dang that seems like a lot of work just to remove a network adaptor.

It's one minute to accomplish.

There's nothing terrifying about it.

Deleting in Hyper-V Manager only deletes the configuration files for the VM not the VHDX files.

So, just run the process.

A backup should be in place anyway right?

Server Crashed before I could do this, so rebuilt it from scratch.