Glasgow: Coal mine won't send coal. What am I missing here?

[KingDingbat]

I have a station that is in range of both the coal mine and the steelworks factory. What I expect to happen is that the coal mine will send coal to the train station and the factory will retrieve it since all 3 buildings are "connected".

But it's not happening. I have trains bringing iron ore from the iron mine to the station, but the coal mine is not sending coal anywhere. I was hoping to do this efficiently without adding a truck line. Am I missing something? Here's a screenshot:
https://i.imgur.com/bvcsUHp.jpeg

[Vimpster]

Transport between facilities without a vehicle involved is not allowed.

The rule is that cargo can only make a single jump in a row. After jumping from facility to station it can not jump again without first being loaded and subsequently unloaded from a vehicle, at which point it can make another single jump before requiring another vehicle, so on and so on.

[Tsubame ⭐]

Factories cannot send products to another factory without a working transport line involved. You will need a truck line to send coal to the iron factory.