This is silly message really.
If you’re getting this error (or something similar) but you also know that you’re running the latest version of the iOS build host:
Build server with address 192.168.0.5 is too old to be used with this version of Xamarin.iOS extension. Double click here to select a new server. Xamarin.iOS Extension
It’s most likely that you have a manual proxy configured in your Windows development machine
Go to your Manual Proxy configuration settings and turn off your manual proxy. Once you’ve done this just double click on the message in Visual Studio and it should connect to your iOS build machine and run fine.