One thing i could imagine from the screenshot is, that there is no direct sea-connection from one coastal city to the tile where your ship is. Try sailing it to the coast of Argos and see if its possible to upgrade it there.
On that pic you have a frigate, they upgrade to battleships and you have to have researched electronics for them.
Did a city state gift you that ironclad? Because if to upgrade a caravel you need to have the right tech (steam power?)
Note that in your screenshot, the Caravel has a ranged attack. In Vanilla Civ5, Caravels were ranged and upgraded to Destroyers (which require Combustion). In later versions, Caravels were melee and upgrade to Ironclads. That probably is the source of your problem.
Gods and Kings, and Brave New World are upgrades, or add-ons, to the original game.