Why does my UE4 crash when I build lighting?

I get this log on swarm agent -
[ERROR] Channel registration failed. Reason: No such host is known
, Callstack: at System.Net.Dns.GetAddrInfo(String name)
at System.Net.Dns.InternalGetHostByName(String hostName, Boolean includeIPv6)
at System.Net.Dns.GetHostEntry(String hostNameOrAddress)
at System.Runtime.Remoting.Channels.CoreChannel.GetMachineName()
at System.Runtime.Remoting.Channels.CoreChannel.GetMachineIp()
at System.Runtime.Remoting.Channels.Tcp.TcpServerChannel.SetupMachineName()
at System.Runtime.Remoting.Channels.Tcp.TcpServerChannel…ctor(Int32 port)
at Agent.AgentApplication.Main(String[] args) in D:\Build++UE4\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealSwarm\Agent\AgentApplication.cs:line 133.

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Hello,

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Thanks