I think there's a serious bug with the rebels. When I mouse over Lilybaeum that's held by Carthagenian rebels, there's no icon allowing me to target it. Then I moused over the rebel garrison army and the sword icon appeared, but when I right clicked, nothing happened. My army simply refused to attack the rebels. The settlement's port is surrounded by Carthaginian, Libyan and Spartan ships, and I think it is under siege by the Carthaginain ships as the besieging navy had skull icons showing siege attrition. Yet, the rebels seem to be replenishing their losses despite being under siege.
Thinking that perhaps it's because I cannot move into neutral units' zones of control, I tested it by declaring war on all three factions surrounding the port but my army still refused to move towards the city to capture it.
So my question is, is a port siege separate from a land siege? Or can coastal cities only be besieged by sea and not land? As there's no mouse over message telling me whether the city is under siege, what could be the problem?