Simply said: since I can send settler to the HQ, I can't trade with merchants exept those like Diedre, Daniel, Finch and Ronnie Shaw. The four choices I have are: "Something else" (close the discussion), "Work at HQ", "Trade" (open the settler inventory) and "Nevermind"(close the conversation). I've tried refreshing the plot. No dices. Reaffecting the settler dosen't work either.