SCS have released version 1.41 for American Truck Simulator and Euro Truck Simulator 2.
TruckersMP is currently NOT compatible with these updates. In order to play TruckersMP, you will need to downgrade your game to the temporary_1_40 branch.
Check out this article for information on how to downgrade your game.
---> Must own an official version of ATS or ETS2
---> Must be 14 years or older (Lower age groups prohibited)
---> Must speak English
---> More than 50 hours in either ATS or ETS2
---> Must have any TMP bans/offenses publicly viewable (for application purposes only)