[2021] Train Stations CC DLC not appearing in game?

On the main menu of the game, does it show as owned on the list of DLCs on the left? If it does, then you are looking for this icon. The CCPs have their own little submenus, so all the assets are in one place. For Train Stations you will see this one under Public Transport, all the way to the right, next to the hubs.

https://i.imgur.com/jcDIMj9.jpg