Rebuild paths. Then rightclick the top of your viewort and check View -> Show Paths. That way you see the connections between the paths. White means perfect; green means almost perfect; blue means traversible but if there is a better way, take that instead; yellow means the path is forced.I see it follows the PathNodes, but still couldnt figure it out, any help?
Hm.
Do you have a trader volume set up (can you purchase items in it when you test your map) and do you have a path leading there?
Are you sure the trader path effect is enabled in the menu?
If this doesn't help you solve the problem, can you upload your map somewhere and send me a link per PM? I promise not to use or publish anything about the map and I will relay possible fixes (should I find any) to you via PM.