It has always been possible. However you need an account on which the game keys are registered with. And you need to connect the account online (online or silent) from time to time, for the player profile synchronization. Note: A pure local account does not allow to play alone, it can only be used f...
When you installed windows, did you install other stuff first before installing Maniaplanet? Because some applications might block some ports, especially server applications, chat and download applications, even WAMPP does... If it appears randomly, perhaps it is because you don't use these applicat...