First of all, Hello
I Serve you some troubleshooting topics;
1. If you own a copy of ETS 2 Also try launch via TruckersMP. Thats easily identify the problems source. (Game or Hardware)
2. Look Audio Settinngs in-game and also check audio output place.
3. If no one solve your problem in the listed above, try uninstall the game.
Warm Regards,