If you see an Overstock error that looks similar to this one:
Errors: The following variation(s) is/ are already associated with another product(s): JPS070, JPS072, JPS073, JPS001, JPS045, JPS023,...
You'll want to either change the market ID in LM to match what OS has.
Change the market ID on OS to match what LM has. (If you go this route, you'll want to click save changes on the listing to re-sync it).