The traders can be fixed by editing the five trader prefab files (data\prefabs\settlement_trader_01.xml through settlement_trader_05.xml). Enable the commented out section by removing "<!--" and "-->" from all five trader prefabs. Also, change the TraderArea property from False to True in the same files.
I recently made these fixes since only two of ten cities I have found so far had traders buildings and both had dead/missing traders when discovered. Without an official fix this is a solution to have traders. Otherwise cash and coin are worthless. I look forward to discovering a living trader.