I wonder if this is the same annoying issue that plagues the existing multi-track stations. It's hit or miss as to which track the station will "allow" receiving outside trains. It's almost never the track I actually want them coming to.
For example, in one game, I tried placing down the multi-track endpoint station, and I connected the right-most line (when looking down at it with tracks pointed up). Waited and waited, no trains. Then I made a connection between that track and the next one over. Then, magically, trains appeared -- only they of course went to the next platform over to what I really wanted.
So I would see if this bug still exists with the new assets. Try connecting different tracks to the outside (assuming it has different tracks; while I've seen screenshots of the new assets, I didn't memorize their names and have not bought the DLC yet).