Since this VM came from a crashed server, it is probably just stuck on its old network settings.
Try these quick steps inside the VM:
Fix IP and DNS: Go to your network settings (IPv4). Change the Default Gateway to match your new network's router IP. Because this is an Active Directory server, keep the Preferred DNS as 127.0.0.1, but add 8.8.8.8 as the Secondary DNS so it can access the internet.
Remove old network cards: Open Command Prompt as Admin, type set devmgr_show_nonpresent_devices=1 and press Enter, then type devmgmt.msc. In Device Manager, click View > Show hidden devices. Look under Network adapters and delete any faded/hidden network cards from the old server.
Reset network: If it still doesn't work, run netsh int ip reset in Admin Command Prompt and restart the VM.
Also, just double-check your Hyper-V Virtual Switch manager on the host to ensure it is set to External and connected to the right network card.