Error 10054 with Photon Server

If I use "Photon Cloud" to run two instances of my app on my home network, they connect fine and I see both players in a scene, etc. If I switch to "Self Hosted" with the IP of my home server running the 64 bit "Load Balancing (MyCloud)" Photon Control, the app instance on the server connects OK, but on the second machine I get:

Receive issue. State: Connected. Server: '' ErrorCode: 10054 SocketErrorCode: ConnectionReset Message: An existing connection was forcibly closed by the remote host.
System.Net.Sockets.SocketException: An existing connection was forcibly closed by the remote host.

at System.Net.Sockets.Socket.Receive (System.Byte[] buffer) [0x00000] in :0
at ExitGames.Client.Photon.SocketUdp.ReceiveLoop () [0x00000] in :0
NetworkingPeer:DebugReturn(DebugLevel, String) (at Assets/Photon Unity Networking/Plugins/PhotonNetwork/NetworkingPeer.cs:1522)
PhotonHandler:Update() (at Assets/Photon Unity Networking/Plugins/PhotonNetwork/PhotonHandler.cs:157)

Photon Control is running as admin and has added the firewall exceptions ok.

Please help!