[Rerun]

I have two Windows 10 machines running mobile sheets and want to sync them. If I run the device sync and set machine A to be the server and machine B to be the client, the app server is assigned to an IPv4 adress and both devices see each other. But if done otherway round and I set machine B to be the server and machine A the client the server is getting an IPv6 adress assigned and remains invisible to the other device.

Why are both machine behaving differently and why are the machines invisible to each other?