TruckersMP does not support the latest game version of Euro Truck Simulator 2 or American Truck Simulator yet.
Check out the following guide on how to downgrade so you can keep playing on multiplayer:
How to downgrade
我们需要喜爱这款游戏的玩家，只要你遵守游戏内的交通规则，不会给车队添麻烦，我们欢迎您。 We need players who love this game. As long as you abide by the traffic rules in the game, you will not cause any trouble to the team. We welcome you.