Weird instant ClientDisconnect

Heya,

I have set up Photon Swarm with a UE4 project and locally, everything works fine. However, when I try to connect remotely, it connects to the master server just fine... but when I try to create a room, this happens on the server side:

2016-11-03 16:31:33,826 [10] DEBUG Photon.LoadBalancing.MasterServer.GameApplication - Created game: gameId=Test Room, appId={Default}
2016-11-03 16:31:33,830 [10] DEBUG Photon.LoadBalancing.MasterServer.Lobby.GameListBase - PlayerCount updated:newValue=1, oldPlayerCount=0, plyaerCount=1
2016-11-03 16:31:33,831 [10] DEBUG Photon.LoadBalancing.MasterServer.Lobby.GameState - Added peer: gameId=Test Room, userId=ee30590c-dd6d-4571-8e4f-7cf71922091e, joiningPeers=1
2016-11-03 16:31:33,831 [13] DEBUG Photon.LoadBalancing.MasterServer.PlayerCache - Player state changed: pid=ee30590c-dd6d-4571-8e4f-7cf71922091e, master=True, gid=Test Room
2016-11-03 16:31:33,833 [10] DEBUG OperationData - SentOpResponse: Peer=T:MasterClientPeer,ConnId:0,ip:185.6.104.142:62745, opCode=227, return=0, ChannelId=0, result=Ok, data=(53 bytes) F3-03-E3-00-00-2A-00-02-E6-73-00-14-31-34-36-2E-32-35-35-2E-31-35-38-2E-31-39-34-3A-35-30-35-36-FF-73-00-11-48-69-67-68-6C-61-6E-64-65-72-27-73-20-52-6F-6F-6D
2016-11-03 16:31:33,881 [16] DEBUG Photon.SocketServer.ApplicationBase - OnDisconnect - ConnID=0 reasonCode=ClientDisconnect
2016-11-03 16:31:33,882 [14] DEBUG Photon.SocketServer.PeerBase - Connection state changed from Connected to Disconnected: peer=T:MasterClientPeer,ConnId:0,ip:185.6.104.142:0
2016-11-03 16:31:33,882 [14] DEBUG Photon.LoadBalancing.MasterServer.MasterClientPeer - Disconnect: pid=0: reason=ClientDisconnect, detail=
2016-11-03 16:31:33,883 [14] DEBUG Photon.LoadBalancing.MasterServer.GameApplication - OnClientDisconnect: peerId=0, appId={Default}
2016-11-03 16:31:33,883 [11] DEBUG Photon.LoadBalancing.MasterServer.Lobby.AppLobby - peer removed from lobby:l:'Photon.LoadBalancing.MasterServer.Lobby.AppLobby',p:'T:MasterClientPeer,ConnId:0,ip:185.6.104.142:0',u:'ee30590c-dd6d-4571-8e4f-7cf71922091e'
2016-11-03 16:31:33,884 [14] DEBUG Photon.SocketServer.PeerBase - Connection state changed from Disconnected to Disposed: peer=T:MasterClientPeer,ConnId:0,ip:185.6.104.142:0

The client receives a 1040 error a while later, but nothing else in between:

PhotonLBC:  2016-11-03 16:31:30,790 INFO    Client.cpp                     ExitGames::LoadBalancing::Client::onOperationResponse()      line:   668 - OperationResponse - operationCode: 227, returnCode: 0
PhotonLBC:  2016-11-03 16:31:30,823 INFO    PeerBase.cpp                   ExitGames::Photon::Internal::PeerBase::connect()             line:   171 - address: 146.255.158.194:5056
PhotonLBC:  2016-11-03 16:31:40,923 INFO    EnetPeer.cpp                   ExitGames::Photon::Internal::EnetPeer::sendOutgoingCommands() line:   172 - disconnect due to retry timeout (max retry time) time: 10109   originalSentTime: 63
PhotonLBC:Error: connection failed with error 1040
PhotonLBC: disconnected

Any help on this matter (or at least how to debug it) would be appreciated. All the ports are forwarded on the host machine, firewalls were turned off on both for good measure as well.

Best regards,
Damir H.