Investigation suggested the issue was with the initial Hyper-V configuration as removing the virtual NIC from the guest allowed it to boot without issue. Re-adding the same virtual NIC reproduced the problem, but adding a new virtual NIC (on a different physical socket in the host) brought back full functionality. Note that as far as the OS is concerned this is a whole new NIC, so you’ll need to manually reconfigure TCP/IP addresses if it was on static entered address before.
Veeam ports for Hyper-V host
If you try and add a Hyper-V host to your Veeam backup infrastructure, without having the correct ports open on the...