Old thread I know but, the problem has to do with not allowing the VEPRO server on the slave through the Windows firewall and on the configuration of the network between the master and the slaves.
On my set up I have to allow the vienna servers (32 and 64 bit) to communicate through the windows defender firewall on the public networks - leaving it to come thorugh only on the private networks prevents the slave server from showing up on the Vienna client plug-in in my DAW.
I am not sure if this is because my netwrok is set to public or not (and I don't have time right now to check) but what I am pretty sure about is that if you let the server come through the windows defender firewal on both private and public networks, chances are you should be right. Let me know.
Also, if anyone has some time - this link show how to check and mess about with the network's private/public setting through Regedit.
https://www.kapilarya.com/switch-network-from-public-to-private-and-domain-windows-10
Cheers.