Fyi: the majority of those tabachi stores have stopped selling tickets for Juve games (in general sale). Since, for many of them, it's just not worth the hassle anymore. A lot of waiting, trying, etc just to end up selling about 10 tickets in total makes no economic sense for them.
If you are in Turin & do not have a ticket, your best bet is the ticket office at the stadium (gate B). But, obviously, when a game is sold out (as will be the case for the Atalanta one) you won't find tickets there either.