Won’t let me download the game on steam???

Hello, I am trying to download hitman 3 on steam, but it will not let me. It only shows me the demo download button and the deadly sins pack, but it isn’t giving me the option to buy the base game. I have already downloaded the demo and I do have the game on epic games, but it has refused to work so I want to get it on steam. How can I buy the base version?