Windows 10 Netclient joins ( via realy) but cannot acces remote LAN

[Elf36]

Hi,
I have set up netclient on a Mac and a windows PC - the Windows PC is on the same LAN as the server (main netclient) I can get LAN access to a server 6000 miles away from my mac but not the PC - also speed is quite slow and not sure why - the windows PC often shows a warning sign -
I have very little to go on - when my mac just works the PC really doesn't