I’m not downloading and running all those mods, but when I load up the game and click on your two market stalls, I see one of them is on cooldown and the other isn’t. When I click “Call Trader” on the one that’s off cooldown, the trader window properly pops up (in this case, it was Gannor’s Breakfast Foods Trunk with a variety of breakfast foods for sale. I just tried it again (reloading the game and clicking the same market stall) and got Vert Greene’s Verdant Greenery with a variety of seeds, etc.
Edit: There’s a whole lot of z-fighting (the graphical flickering) going on with the floor of your main fortress structure. Did you insta-build that by any chance? It seems that the terrain for the foundation didn’t get dug out so they’re overlapping.
Edit 2: I let it run on speed 3 for about a day so the timer on the other market stall would reset, and successfully used that as well. One thing to keep in mind is that if you have a dialog open, like the daily update dialog, the alert and dialog for the trader won’t pop up until you close the other one.