Stupid Harbor question...

I just noticed that I've been going my whole game without one of my cities connected by a City Connection, no idea why. I'm on an island, 2 of my cities and my capitol have Harbors. But only 1 has the City Connection icon. What am I missing?

I was going to attach a screenshot, but all I'm getting is a solid black image. Will have to resolve that too

Screenie would help , but this can happen if the harbor connection to that city is interrupted by fog, an intervening AI civ without open borders, or a barb sitting on a tile in the only available coastal path from that city to either your capital or the other city with a harbor (the harbor connections can chain their way from city to city before connecting to your capital, but it has to be a fully navigable chain). Not usually a problem once you've researched Astronomy.

Okay...Well, it just connected. Like 50 turns after I circled my island and could see a ring of water around. I don't get what triggered it. It's not coast visibility, there's still 2 hexes that are technically covered in fog even though I can see the water underneath. And I've seen coast+ocean around for most of the game.

Ah, I didn't know a barb boat could block it, I normally do land games or don't watch that the icon appears/disappears mid game There was a barb boat sitting on my coast the last few turns.

I don't think that it actually has to be navigable.

I was unlucky enough to found Rome on part of the ocean completely encircled by ice outside of my view for several turns, but a harbor by itself still connected me to my coastal cities without first building a road to one.

EDIT: When an enemy unit disrupts the route, you get a half red version of the connection icon. I think that is only after it's established to begin with, though.