Probably all this will fall into deaf ears once more. I have had the problem for very long, since one of the SP's of 09. And I have learn to live with it.
Try this: Install the asset (the MIN with the red arrows) new anywhere, connected or not to tracks. Now open the menus and set ONE commodity, lets say a lumber product from the built in commodities. The go to tracks and you should see it available, click to it and set any variation of load or unload or both. Save and open your route. Verify it is there and the commodity is available. If it works, proceed to populate with one more commodity each time. If the asset fails to operate as expected, contact help desk and inform them: "A built in asset does not work" with all the details.
I have made this asset to work, but the ones with the green arrows, accept only 4 commodities. Try to add another one, and it freezes for good, and you have to re-install. This is not a case of faulty commodity asset: As a draconian solution I deleted ALL the assets/commodities time ago, and then I populated only the ones that could not be deleted because they are built in: Same problem! Sorry if I am blunt about it, but enough is enough, as N3V does not even, ever commented on this World wide recurrent problem.