It might be a driver issue.
- Boot into macOS.
- Open Boot Camp Assistant again, and from the Action menu (or toolbar), choose Download Windows Support Software.
- This will download the correct drivers, including for your network adapter, onto a USB drive.
- Reboot into Windows 10.
- Plug in the USB stick. Open it and run Setup.exe from the WindowsSupport folder.
- Let it install all the needed drivers, especially for Wi-Fi and Ethernet.
- Restart Windows and try connecting again.
If that doesn't work, then I think the only option is to remove Windows 10.