can't establish trade route to certain civs-possible reasons?

[mzprox]

Sorry I can't post a save right now, just interested what could be the reason i can't make trade routes to certain civs.

-neither land nor sea trade routes (those civs are not appear on the list)
-I have open border (not sure if it prerequisity, but i have anyway)
-I can make trade routes with other civs, even across those civ's territories I could not trade with
-It's quite late in the game (future techs and such, I was just waint to get culture victory)

any idea? maybe a bug?

 

[Hakan-i Cihan]

This can be caused by the following reasons:

• 
  The cities of the civ is out of range. Caravans have a range of 10 tiles which can be extended by building caravanserai or roads. Cargo ships has range of 20 tiles which can be increased by a harbor.

• You ar at war with those civs.

• With world congress civs can be embargoed, so that no civs can establish trade routes with those civs.

 

[mzprox]

Oh, it should be the embargo thing, thank you

 

[ThorHammerz]

• 
  The cities of the civ is out of range. Caravans have a range of 10 tiles which can be extended by building caravanserai or roads. Cargo ships has range of 20 tiles which can be increased by a harbor.

As a side note, the acquisition of certain technologies also provide range increases (applied before harbor/caravansary multiplier) to trade routes.

 

[Primacide]

Trade embargoes are among the most common world congress proposals put forward by the AI. They also frequently pass. I know I rarely intervene or waste votes swinging it, so the early warmonger frequently winds up embargoed. It's a pain when you're going for a culture victory and could really use the extra tourism bonus for having a trade route.