Hey,
You see players on the map only in a certain radius around you.
If you don't see a player, there is no player near you. There are areas with less or no traffic and areas with a lot (Duisburg/Calais).
If you don't find any players in Duisburg, for example, I recommend you to reinstall TruckersMP and try to verify your game files on steam.
Verify game files:
Right click on game, select properties, goto local files tab and press verify game files.
I hope my answer could help you.
Best regards
DrewK
and also thank you! 
