I'd start with the normal troubleshooting steps:
1) can you ping the K2 server you're trying to register form the machine where you are running K2 service manager from?
2) is the K2 server service running on the K2 server machine?
3) can you register the server in K2 service manager when you run Service Manager on the K2.net server itself?
4) are there any firewalls between this machine and the K2.net server?
5) which version of K2.net is running on the server and on the machine where you are trying to use Service Manager?
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