You are right about the CB being ON by default, and in channel 19. Check MP settings (the small cog in the lower left corner of the Players Near You window) and see if in General, you have "Default CB radio channel" in 19 (it can be changed). Maybe that space is blank, never seen it like that, but I can't think of anything else. Other than doing a repair or clean reinstall of the TMP launcher. To try the easiest way, run the launcher and hit F1, so it will download all files again. If that doesn't work, you can also try uninstalling the launcher, then go to C:\Program Data\ and delete the TruckersMP folder. Then download from the website and install again.