Sorry about that, was not aware of any region lock. And, truth be told, I just learned today that this is, apparently, information intentionally not really shared by Humble, for example.

I had this issue with two other keys now (and one is allegedly not even region locked? Who knows what fuckery is going on here), I'll have a discussion with the mods about this, to see how I should deal with stuff like this in the future..

Took me some digging, but I at least found the restrictions for this specific key (Well, in theory. No idea how to really confirm this).
https://steamdb.info/sub/867239/

So, looks like it's basically an EU only key

I'll send you a friend invite via Steam (Steam is not working right now, at least for me?!), to send you the game via gift.