Unlike ProMods on Euro Truck Simulator 2, with ProMods Canada on American Truck Simulator, you're able to play on any of the servers.
I'd recommend you checkout this Knowledge Base article on how to install ProMods Canada for TruckersMP:
https://truckersmp.com/kb/1122
Please ensure you have downloaded all the required files, you have not edited the names of the files and they're installed in the correct location.
If you continue to have issues, I'd recommend you share a screenshot of your mods folder, so we can see if everything is set up correctly.