Are you familiar with using Wireshark for traffic analysis? I think the next step is to figure out what is getting through and what isn’t, to the Windows machine to start with.
Focusing on IPv4 for now, I would hope the network trace shows the DHCP request being sent out, the DHCP response with an IP for the Windows machine, and then some outbound web TCP traffic (eg google.com), followed by some sort of TCP response. But since it’s not working, I imagine the latter would be replaced by – ideally – ICMP error messages that will describe the problem.