Looking at your account via the game API, you do not have Shadowkeep or the Shadowkeep Deluxe Edition.
The purchase of Shadowkeep does entitle you to one season pass. This season pass would be applied immediately on purchase. The Shadowkeep Deluxe Edition, which was available until the launch of Season of Dawn in December, had 4 season passes included.
I did buy Shadowkeep on Xbox then I bought the season pass on Steam, but I don't get how I got 3 seasons with one season pass and then at the second purchase I get only one... And once again a friend of mine said that I should've had 4 of em since he did..
I don't really want to be a bother, but I find it a bit odd to have to buy it again..