Why won't this dock produce grain?

As can be seen in the image below, the ship can access both docks.

Solution 1:

Just so we have an answer here:

In order for a resource to produce, the station/dock/loading bay attached to it needs to have been visited by a transporter fitted out to carry that type of resource. In this instance, a ship must have visited the dock that has been fitted out to carry grain.

Once that has happened, the resource will start delivering produce to your dock.

This can be altered by the settings in the station window by chaning Deliver cargo to a station only when there is a demand (under cargo handling) to Off