I already checked it. there are no download in ‘my steinberg’, but only reactivation button.
Cubase AI 6 is so old type app. It wasn’t served to download code, just to DVD. also support center has only AI 7, 8, 9, 10 series.
https://www.steinberg.net/forums/viewtopic.php?t=98677
in this forum, so many people had same problem with me…