I recently got Rainbow Six: Siege and today I found out that I have to install the game as it seems that I don't have it installed. After looking through a couple folders I located it and it seems to be in the steamapps/common folder and all of it is there. I'm very confused to why steam wants be to essentially reinstall the game even though it's there. I've looked online and haven't found a solution after many attempts. Could anyone please help me?