If an enemy fleet is parked on your citadel, you can't fire any missiles. The normal options for that world are "Designate, deploy, import from, missiles." With an enemy fleet in orbit, the option of "attack" is created, which makes the "missile" option unclickable since its too far down on the interface.

george moromisato 10 Mar 2017:

This would also be a problem at T&E empire on a trade hub with an enemy fleet (because we add a Sell To button).

I've fixed this by adding the Import From button to the Structures tab. The duplicate Import From button on the default tab will get replaced as appropriate.