Hi @Ryuichi
Please Follow this step's:
1-) Go to Documents and Delete the ETS2MP Folder
2-) Press the Windows Key + R (Win+R) on your keyboard
3-) Enter "%programdata%" and press Enter (Without the quotes)
4-) Find the folder "TruckersMP" and delete that folder.
5-) Navigate to C:\Program Files\ and delete the folder named "TruckersMP Launcher"
6-) And, go to re/download this launcher here: https://truckersmp.com/download