Hello the first thing i would like to say to you is to go in your steam library then go into euro truck simulator 2 properties > betas> opt out of all betas then wait if that doesn't work install a different patch then click on opt out of all betas and that might work if that doesn't work try and install the launcher again and if not that re install both the launcher and ets2. I hope i helped.
For more help make a ticket - support.truckersmp.com
Best regards Misiek