Over the course of multiple playthroughs in both singleplayer and multiplayer through the past few patches i have not been able to trigger the International trade civic. In past games I thought it was because one or more empires had been eliminated from the game thus making it impossible for anyone to get, but in my last game i made sure to leave every player alive and have a trade route with each of them and the civic still wouldn't trigger despite me earning the steam achievement for having trade routes with 8 empires (everyone in the game) and having 18 merchant stars. This severely hurt my economy when going to war with other trade powers. One note was that often in these games at least one or more empires was vassalized since that has been normal in my high difficulty games with AI, which may also be the issue. 

Maybe change the prerequisite to having a trade route with all surviving/active empires? I just want to use the civic again.