Fezz [AE]'s post in Auto-reconnection does not work was marked as the answer
Yes, when the connection to the server is interrupted for some reason, it tells you that it will automatically reconnect you again, and nothing happens. This happens to everyone. You have to rejoin again in a manual way, unfortunately.
Fezz [AE]'s post in Changing the steam account linked to Truckersmp was marked as the answer
Unfortunately, your Steam Account connected to your TruckersMP account cannot be changed. If so, you have a new Steam Account then you have to make a new TMP account. Hope that answers your question!