This one's pretty weird and annoying, Truckers MP doesn't recognize my wheel at all, meanwhile it works like a charm in singleplayer, I had this same problem about an year ago and stopped playing because i couldn't fix it.
I've tried all the obvious things, re-installing drivers, re-installing the game, restarting my PC (obviously) replugging the wheel in, re-installing the logitech gaming software, looking into firewall to see if Truckers MP doesn't have access to something, it does.
I'm out of options honestly, this doesn't make any sense either why it wouldn't work in multiplayer.