Hello there @ExTee,
I will give you two steps to follow and let us know if your issue is resolved.
Step 1: Verify your ETS2 files in steam. [Right Click ETS2 ➜ Properties ➜ Verify integrity of game files...]
Step 2: Delete & Uninstall TruckersMP by following these steps:
1. Press the Windows Key + R (Win+R) on your keyboard
2. Type "%programdata%" and press Enter (without the quotes)
3. Find the folder "TruckersMP" and delete that folder.
4. Navigate to C:\Program Files\ and delete the folder named "TruckersMP Launcher"
5. Navigate to Documents and delete the folder named "ETS2MP"
6. Press the Windows Key + R (Win+R) on your keyboard & type "regedit", expand HKEY_LOCAL_MACHINE and expand SOFTWARE and delete the "TruckersMP" file
7. Go to TruckersMP website and re-download and install the Launcher with admin privileges https://truckersmp.com/download/
8. Open The Launcher with admin privileges and click "Install Available Updates"