Stuart (GB)

Try the following:

Solution 1:
> Goto C:\ProgramData\TruckersMP
> Delete both core_ets2mp.dll  files
> Start Truckersmp launcher as administrator and click on install the files.

Solution 2:
> Press the Windows Key + R (Win+R) on your keyboard
> Enter "%programdata%" and press Enter (without the quotes)
> Find the folder "TruckersMP" and delete that folder.
> Navigate to C:\Program Files\ and delete the folder named "TruckersMP Launcher"
> Go to our website and re-download and install the Launcher with admin privileges https://truckersmp.com/download/
> Open The Launcher with admin privileges and click "Install Available Updates

Solution 3:
> Download Ultrasurf.
> Run Ultrasurf.
> Open TruckersMP in Administrator Mode.
> Install the available updates (only the first run with Ultrasurf), wait for it to finish and Launch button appears.
> Exit Ultrasurf

Also, read this topic:

By the way, why you've temporary 1.34? You don't need any beta versions.