>>17229667You're turning off the wrong 3DS, or starting the trade with the wrong one.
It goes like this:
>3DS Black has Arceus.>3DS Red has Bunnelby.>Red requests that Black trades.>Black accepts.>Red offers Bunnelby.>Black offers Arceus.>Trade commences.>Red receives Arceus.>Black receives Bunnelby.>Communications begin.>~4.5 seconds in, turn off Black.>Any time after, turn off Red.At that point, if all went well, both Red and Black have Arceus.