I have just migrated PRTG from a working server to a new one, following the method on the PRTG knowledge base exactly. Once complete, I disconnected the original server from the network and connected the new one. All of the network was displayed, although only two groups of sensors were 'active', everything else remained greyed out. I disconnected the server from the network to check the settings and reconnected the original server. When this started up, all of the OTHER sensor groups were active (green), whilst the ones active on the new server were greyed out. I also recieved an email from PRTG after migration was complete saying:
This e-mail was sent by your network monitoring system "PRTG Network Monitor (WIN-8R0IO39MOTH)". There is something that you need to pay attention to:
ToDo: License Error Subject: License already in use
Your license key is already used by another computer in your network, but non-site-license keys may only be used on one PC. PRTG will now run as Freeware Edition.
Please review all ToDos at http://192.168.1.63/todos.htm
Any help would be greatly, greatly appreciated.