Can't get thin clients to work.

[agentkoos]

I have tried everything I found in the manuals and online but I'm stuck. I'm running Windows 10 and NComputing RX300 thin clients.
I'm using Key file authentications. I tried network discovery plugin and backend. Also tried manually adding clients and Builtin backend:
Win10-PC3:11100
Win10-PC3:11101
Win10-PC3:11102
etc.
Only the Master server shows and the Thin client server.