This was mentioned within the discord by @CJMAXiK
New version incompatibility
We are aware that SCS Software has released an update for both American Truck Simulator and Euro Truck Simulator 2. If you happen to update the game, it won't work for TruckersMP. As of now, there is no way to downgrade to previous version.
There is no ETA for new version support, your patience is appreciated whilst we working on supporting the new version.