You are not providing a network id from the stations and have not changed the default setting for network id.
Settings -> Mod Settings -> Map -> LTN - Logistic Train Network -> "Default network ID". Change it away from 0 , e.g. to 1.
I will add even more of a FAQ to the readme.
Q: WHY WAS THE DEFAULT NETWORK ID VALUE CHANGED FROM -1 (before 2.2.0) TO 0?
A: Before 2.2.0, if a station provided any signals (provider, requester, items etc.) to a LTN train stop but did not provide a "LTN Network ID" signal, then this station was automatically considered in all networks and LTN would send trains from any network to that stop, because the default of -1 meant "all networks". This was especially problematic when using the LTN Combinator and turning it off. The station would still receive any non-LTN specific signal but none of the LTN signals that come out of that combinator and suddenly trains would show up at the stop. With the default value of "0", the player has to explicitly enable the network that at station belongs to (by sending a network id signal) or changing the default value.
