I got a Silvally code in a trade a few days ago, but the game keeps telling me that I can't receive a gift for it. I looked on the official site, and it says that the codes will work in Sun or Moon until February, but doesn't mention USUM at all. This leads me to believe that, perhaps these codes don't work in USUM, but I'd like confirmation. I've become the champion, but have done almost none of the postgame missions.