I have been trying to get ats going on my server as well and it is a fresh install on my server and I do have the same problem with the main game port not listening as well and yes I did follow American Truck Simulator / Euro Truck Simulator 2 Guide
as well as
Documentation/Tools/Dedicated Server - SCS Modding Wiki
so i don’t know what is going on and ufw does show the ports are there and ampinstmgr ports show that one port is closed