I have installed an agent on windows with the option "ServerConnection = <some ip>". At start it make connection the the server and actived a tunnel. Bus after some minutes the download certificates are saved. As soon the certificates are saved, the connection doesn't work anymore. 
2018.01.05 14:17:20.812 *I* Successfully registered on management server <server ip>
2018.01.05 14:17:20.813 *D* [tunnel ] Tunnel manager started
2018.01.05 14:17:20.822 *D* [tunnel ] <server ip>: Cannot open file "<some path>\nxagentd\certificates\CAD4EAF5F8DCF4FCEA57D70611528A9EEBE98007.crt" (No such file or directory)
2018.01.05 14:17:20.822 *D* [tunnel ] <server ip>: Cannot open file "<some path>\nxagentd\certificates\060285B36125000000000000000000000000.crt" (No such file or directory)
2018.01.05 14:17:20.836 *D* [tunnel ] <server ip>: Server certificate subject is <some data>
2018.01.05 14:17:20.836 *D* [tunnel ] <server ip>: Server certificate issuer is <some data>
2018.01.05 14:17:20.837 *D* [VCS-1] Requesting parameter "System.PlatformName"
2018.01.05 14:17:20.837 *D* [VCS-1] GetParameterValue(): result is 0 (SUCCESS)
2018.01.05 14:17:20.837 *D* [VCS-1] Requesting parameter "System.UName"
2018.01.05 14:17:20.837 *D* [VCS-1] GetParameterValue(): result is 0 (SUCCESS)
2018.01.05 14:17:20.838 *D* [tunnel ] <server ip>: Sending message CMD_SETUP_AGENT_TUNNEL
2018.01.05 14:17:20.842 *D* [tunnel ] <server ip>: Received message CMD_REQUEST_COMPLETED
2018.01.05 14:17:20.842 *D* [tunnel ] <server ip>: Tunnel is active
2018.01.05 14:17:21.813 *D* [db.query ] {0000017DCADD11E0} Successful prepare: "SELECT value FROM registry WHERE attribute=?" [0 ms]
2018.01.05 14:17:21.813 *D* [db.query ] {0000017DCADD11E0} bind at pos 1: "upgrade.file"
2018.01.05 14:17:21.814 *D* [db.query ] Successful prepared sync query: "SELECT value FROM registry WHERE attribute=?" [0 ms]
2018.01.05 14:17:21.815 *D* [db.query ] Successful sync query: "SELECT guid,type FROM agent_policy" [0 ms]
2018.01.05 14:17:21.816 *I* NetXMS Agent started
2018.01.05 14:17:50.843 *D* [tunnel ] <server ip>: Sending message CMD_KEEPALIVE
2018.01.05 14:17:50.847 *D* [tunnel ] <server ip>: Received message CMD_KEEPALIVE
2018.01.05 14:17:58.419 *D* [tunnel ] <server ip>: Received message CMD_BIND_AGENT_TUNNEL
2018.01.05 14:17:58.511 *D* [tunnel ] <server ip>: Sending message CMD_REQUEST_CERTIFICATE
2018.01.05 14:17:58.518 *D* [tunnel ] <server ip>: Received message CMD_NEW_CERTIFICATE
2018.01.05 14:17:58.529 *D* [tunnel ] <server ip>: Certificate and private key saved
2018.01.05 14:17:58.529 *D* [tunnel ] <server ip>: Sending message CMD_REQUEST_COMPLETED
2018.01.05 14:17:58.533 *D* [tunnel ] <server ip>: Received message CMD_RESET_TUNNEL
2018.01.05 14:17:58.534 *D* [tunnel ] <server ip>: Receiver thread stopped (tunnel reset)
2018.01.05 14:18:20.573 *D* DataCollector: sleeping for 60 seconds
2018.01.05 14:18:20.848 *D* [tunnel ] <server ip>: Resetting tunnel
2018.01.05 14:18:20.863 *D* [tunnel ] <server ip>: Certificate and private key loaded
2018.01.05 14:18:20.881 *D* [tunnel ] <server ip>: TLS handshake failed (error:00000001:lib(0):func(0):reason(1))
2018.01.05 14:18:50.892 *D* [tunnel ] <server ip>: Certificate and private key loaded
2018.01.05 14:18:50.909 *D* [tunnel ] <server ip>: TLS handshake failed (error:00000001:lib(0):func(0):reason(1))
2018.01.05 14:19:20.573 *D* DataCollector: sleeping for 60 seconds
				
			2018.01.05 14:17:20.812 *I* Successfully registered on management server <server ip>
2018.01.05 14:17:20.813 *D* [tunnel ] Tunnel manager started
2018.01.05 14:17:20.822 *D* [tunnel ] <server ip>: Cannot open file "<some path>\nxagentd\certificates\CAD4EAF5F8DCF4FCEA57D70611528A9EEBE98007.crt" (No such file or directory)
2018.01.05 14:17:20.822 *D* [tunnel ] <server ip>: Cannot open file "<some path>\nxagentd\certificates\060285B36125000000000000000000000000.crt" (No such file or directory)
2018.01.05 14:17:20.836 *D* [tunnel ] <server ip>: Server certificate subject is <some data>
2018.01.05 14:17:20.836 *D* [tunnel ] <server ip>: Server certificate issuer is <some data>
2018.01.05 14:17:20.837 *D* [VCS-1] Requesting parameter "System.PlatformName"
2018.01.05 14:17:20.837 *D* [VCS-1] GetParameterValue(): result is 0 (SUCCESS)
2018.01.05 14:17:20.837 *D* [VCS-1] Requesting parameter "System.UName"
2018.01.05 14:17:20.837 *D* [VCS-1] GetParameterValue(): result is 0 (SUCCESS)
2018.01.05 14:17:20.838 *D* [tunnel ] <server ip>: Sending message CMD_SETUP_AGENT_TUNNEL
2018.01.05 14:17:20.842 *D* [tunnel ] <server ip>: Received message CMD_REQUEST_COMPLETED
2018.01.05 14:17:20.842 *D* [tunnel ] <server ip>: Tunnel is active
2018.01.05 14:17:21.813 *D* [db.query ] {0000017DCADD11E0} Successful prepare: "SELECT value FROM registry WHERE attribute=?" [0 ms]
2018.01.05 14:17:21.813 *D* [db.query ] {0000017DCADD11E0} bind at pos 1: "upgrade.file"
2018.01.05 14:17:21.814 *D* [db.query ] Successful prepared sync query: "SELECT value FROM registry WHERE attribute=?" [0 ms]
2018.01.05 14:17:21.815 *D* [db.query ] Successful sync query: "SELECT guid,type FROM agent_policy" [0 ms]
2018.01.05 14:17:21.816 *I* NetXMS Agent started
2018.01.05 14:17:50.843 *D* [tunnel ] <server ip>: Sending message CMD_KEEPALIVE
2018.01.05 14:17:50.847 *D* [tunnel ] <server ip>: Received message CMD_KEEPALIVE
2018.01.05 14:17:58.419 *D* [tunnel ] <server ip>: Received message CMD_BIND_AGENT_TUNNEL
2018.01.05 14:17:58.511 *D* [tunnel ] <server ip>: Sending message CMD_REQUEST_CERTIFICATE
2018.01.05 14:17:58.518 *D* [tunnel ] <server ip>: Received message CMD_NEW_CERTIFICATE
2018.01.05 14:17:58.529 *D* [tunnel ] <server ip>: Certificate and private key saved
2018.01.05 14:17:58.529 *D* [tunnel ] <server ip>: Sending message CMD_REQUEST_COMPLETED
2018.01.05 14:17:58.533 *D* [tunnel ] <server ip>: Received message CMD_RESET_TUNNEL
2018.01.05 14:17:58.534 *D* [tunnel ] <server ip>: Receiver thread stopped (tunnel reset)
2018.01.05 14:18:20.573 *D* DataCollector: sleeping for 60 seconds
2018.01.05 14:18:20.848 *D* [tunnel ] <server ip>: Resetting tunnel
2018.01.05 14:18:20.863 *D* [tunnel ] <server ip>: Certificate and private key loaded
2018.01.05 14:18:20.881 *D* [tunnel ] <server ip>: TLS handshake failed (error:00000001:lib(0):func(0):reason(1))
2018.01.05 14:18:50.892 *D* [tunnel ] <server ip>: Certificate and private key loaded
2018.01.05 14:18:50.909 *D* [tunnel ] <server ip>: TLS handshake failed (error:00000001:lib(0):func(0):reason(1))
2018.01.05 14:19:20.573 *D* DataCollector: sleeping for 60 seconds