This is the latest patch:
https://forums.ootpdevelopments.com/...d.php?t=359379
It will download an .exe file that looks just like the original game installation itself because it essentially is. Anyway, double-click and install it as if it were your initial purchase. It won't erase your save.
Things having to do with Trading are on the League Settings>Rules tab, upper right but the fact you are in challenge mode worries me that you won't be able to edit anything, so here's hoping the patch helps.