This morning, no idea why, trying to compile a Xamarin.iOS app resulted in an error “Xamarin build server is tool old…” apparently without any reason since nothing has changed on my machine during the weekend. Tried also connecting to a different Mac machine but error was still there while compiling using Xamarin Studio on the Mac machine was ok.
After some investigation I’ve found the solution: looks like that “someone” changed my proxy settings (probably Fiddler) and that was causing the weird message.
Turning it off did the trick.
Hope this will help you in case you see this weird message too.