Advice on trade routes

[Servius Tullius]

Playing as ERE I have just lost sea trade with the WRE yet I cannot see why. There are no enemy navies blockading the WRE and all of Italy is still under Roman rule. I know I've probably overlooked something so I was wondering if anyone could point out what I may have missed that's causing it.

[GussieFinkNottle]

It's not fully clear what's happened. Have they ended the trade agreement, has the income stopped or are you actually unable to propose trade, with no possible route? If it's the last of the 3, remember the requirements for sea trade are that you both have ports in the same body of water, and there is a land route through your territory from your port to your capital, and a land route through their territory to their capital from their port.

If you still can't propose sea trade, it's a bug.

[Slaists]

A land siege of Genoa or Mediolanum would interrupt the trade route.

The original trade route goes from Constantinople to Genoa then to Mediolanum. AI's often raid it or lay siege to those cities. If Genoa gets detroyed the route reroutes through Ravena.

Has the trade route disappeared from the map or is just blockaded? If it still exists on the map, the tooltip should tell if you if it is blockaded anywhere.

[Aeratus]

Trade routes by sea are pretty easy to spot because they show up as a dotted line in the ocean. Maybe you can reload an earlier save to see the dotted line, and then look to see if anything is blocking it in the current turn.

[Bramborough]

I think by far the most likely explanation is that someone has beseiged Mediolanum or Genua. That's happened to me a couple of times in my current ERE campaign. The WRE trade is important enough that I've found it worthwhile to station an army between the two cities (there's a spot next to the river where one army can reinforce either city).