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
Last night (12/07/19) we carried out a convoy to celebrate Courtz49's 5 years of streaming, here's what you said!
18 Apr 17:32 UTC | iHobbit