I've been struggling to setup Hyper-V networking on a laptop for a while now. Until recently I was able to work around it, and not actually solve the problem.

Its well documented, that sharing a Wireless network card in Hyper-V wont work. Since Windows 10 1709, a nifty 'Default Switch' has been provided to help VMs connect to the network via NAT using the hosts default connection. I could only ever get this to work intermittently. Why? Metric.

I believe this has something to do with my specific setup, so I'll outline that too. I use my laptop in three primary modes.

1. Docked which has multiple DisplayPort, USB, 3.5mm, and Ethernet ports, but I use wireless networking
2. Totally mobile, not connected to anything but power, obviously wireless.
3. USB-C Dock with HDMI and USB, again wireless networking.

Eventually I came to notice that it worked when I was not docked. As a diagnostic step I disabled the unused Ethernet connection, and things started working. This told me there was some issue with determining which connection the VM should use.

I set the Metric on my Wireless connection to 1, on my Virtual Adapter (VPN) to 2, and my Wired Ethernet to 50. Things have been working great since. Go figure.

Adapter Settings => IPv4 Properties => Advanced => Uncheck Automatic metric, and specify a value.