I was informed that there are some problem with the mod where they are unable to call for trade caravans due to the “faction leader unavailable”.
Finally, after some digging, the problem is finally resolved.
You can download the updated mod here:
NON-STEAM DOWNLOAD: http://walkingproblem.com/sdm_downloads/trading-economy-ver1-4/
STEAM DOWNLOAD: https://steamcommunity.com/sharedfiles/filedetails/?id=1130945311