I am experiencing the same issue, I tried adding more connections but didn't work. It could be something to do with Traffic Manager based on what I've read but I am not sure.

@juhaszb.2005 I tested it a few times and I don't seem to have any connection issues, if you're still looking to fix it maybe try to subscribe to the mods I listed in the description and make new connections in-game? (I'm making a more detailed version of this exact map right now so maybe you can wait for that as well)

I downloaded all the necessary mods and recommended monds, but cars can't enter the city area and residents can't move in.