It seems that the program may be blocked by a firewall and is not allowed to authenticate your account with the master server, I would suggest that you add Blockland to your allow list in whichever firewall you are using, there is a firewall built into Windows that may be causing the problem if you have strict security settings.
Or in the worst case scenario; you have hacked the demo, and it won't let you play online because you don't have a key.