no trade route avaible

I want to connect to a city state on my continent for a quest in modern era. I have unit, slot avaible and everything ready to go with it being in range of many cities including the home of the unit but the CS does not appear in trade route overview. Can any body help me figure this out?

Check the World Council and make sure they didn't pass an Embargo on City states.

Note that it's not a bug if you just the quest, as you can still fulfill it by first getting the World Council to repeal the embargo.